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Cancer is a group of diseases involving abnormal cell growth with the potential to invade or
spread Spread may refer to: Places * Spread, West Virginia Arts, entertainment, and media * ''Spread'' (film), a 2009 film. * ''$pread'', a quarterly magazine by and for sex workers * "Spread", a song by OutKast from their 2003 album ''Speakerboxxx/T ...
to other parts of the body. These contrast with
benign tumor A benign tumor is a mass of cells (tumor) that does not invade neighboring tissue or metastasize (spread throughout the body). Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have re ...
s, which do not spread. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained
weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat ( adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...
, and a change in
bowel movements Defecation (or defaecation) follows digestion, and is a necessary process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces from the digestive tract via the anus. The act has a variety of names ranging f ...
. While these symptoms may indicate cancer, they can also have other causes. Over 100 types of cancers affect humans.
Tobacco use Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or simply released from the mouth, as is generally done with pipes and cigars. The practice is believed ...
is the cause of about 22% of cancer deaths. Another 10% are due to
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
, poor
diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...
, lack of physical activity or
excessive drinking Alcohol abuse encompasses a spectrum of unhealthy alcohol drinking behaviors, ranging from binge drinking to alcohol dependence, in extreme cases resulting in health problems for individuals and large scale social problems such as alcohol-r ...
of alcohol. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. In the developing world, 15% of cancers are due to infections such as ''
Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is thoug ...
'',
hepatitis B Hepatitis B is an infectious disease caused by the '' Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. ...
, hepatitis C,
human papillomavirus infection Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...
,
Epstein–Barr virus The Epstein–Barr virus (EBV), formally called ''Human gammaherpesvirus 4'', is one of the nine known human herpesvirus types in the herpes family, and is one of the most common viruses in humans. EBV is a double-stranded DNA virus. It is b ...
and
human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immun ...
(HIV). These factors act, at least partly, by changing the
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s of a cell. Typically, many genetic changes are required before cancer develops. Approximately 5–10% of cancers are due to inherited genetic defects. Cancer can be detected by certain signs and symptoms or screening tests. It is then typically further investigated by medical imaging and confirmed by
biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a dise ...
. The risk of developing certain cancers can be reduced by not smoking, maintaining a healthy weight, limiting alcohol intake, eating plenty of vegetables, fruits, and
whole grain A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm. As part of a general healthy diet, consumption of whole grains is associated ...
s, eating
resistant starch Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods, but it can also be added as part of dried raw foods, or use ...
,
vaccination Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...
against certain infectious diseases, limiting consumption of
processed meat Processed meat is considered to be any meat which has been modified in order to either improve its taste or to extend its shelf life. Methods of meat processing include salting, curing, fermentation, smoking, and/or the addition of chemical pr ...
and
red meat In gastronomy, red meat is commonly red when raw and a dark color after it is cooked, in contrast to white meat, which is pale in color before and after cooking. In culinary terms, only flesh from mammals or fowl (not fish) is classified as ...
, and limiting exposure to direct sunlight. Early detection through screening is useful for
cervical In anatomy, cervical is an adjective that has two meanings: # of or pertaining to any neck. # of or pertaining to the female cervix: i.e., the ''neck'' of the uterus. *Commonly used medical phrases involving the neck are **cervical collar **cerv ...
and colorectal cancer. The benefits of screening for breast cancer are controversial. Cancer is often treated with some combination of
radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...
, surgery,
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
and
targeted therapy Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment ( pharmacotherapy) for cancer, others being hormonal therapy and cytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks ...
. Pain and symptom management are an important part of care.
Palliative care Palliative care (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...
is particularly important in people with advanced disease. The chance of survival depends on the type of cancer and extent of disease at the start of treatment. In children under 15 at diagnosis, the
five-year survival rate The five-year survival rate is a type of survival rate for estimating the prognosis of a particular disease, normally calculated from the point of diagnosis. Lead time bias from earlier diagnosis can affect interpretation of the five-year surviva ...
in the
developed world A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
is on average 80%. For cancer in the United States, the average five-year survival rate is 66%. In 2015, about 90.5 million people worldwide had cancer. In 2019, annual cancer cases grew by 23.6 million people and there were 10 million deaths worldwide, representing over the previous decade increases of 26% and 21%, respectively. The most common types of cancer in males are
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, malign ...
, prostate cancer, colorectal cancer, and stomach cancer. In females, the most common types are
breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...
, colorectal cancer,
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, malign ...
, and cervical cancer. If
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
other than melanoma were included in total new cancer cases each year, it would account for around 40% of cases. In children, acute lymphoblastic leukemia and brain tumors are most common, except in Africa, where
non-Hodgkin lymphoma Non-Hodgkin lymphoma (NHL), also known as non-Hodgkin's lymphoma, is a group of blood cancers that includes all types of lymphomas except Hodgkin lymphomas. Symptoms include enlarged lymph nodes, fever, night sweats, weight loss, and tirednes ...
occurs more often. In 2012, about 165,000 children under 15 years of age were diagnosed with cancer. The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries. Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world. The global total economic costs of cancer were estimated at
US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
1.16 trillion per year .


Etymology and definitions

The word comes from the ancient Greek , meaning 'crab' and 'tumor'. Greek physicians
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...
and
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
, among others, noted the similarity of crabs to some tumors with swollen veins. The word was introduced in English in the modern medical sense around 1600. Cancers comprise a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. They form a subset of
neoplasm A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s. A neoplasm or tumor is a group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely. All tumor cells show the six hallmarks of cancer. These characteristics are required to produce a malignant tumor. They include: * Cell growth and division absent the proper signals * Continuous growth and division even given contrary signals * Avoidance of
programmed cell death Programmed cell death (PCD; sometimes referred to as cellular suicide) is the death of a cell (biology), cell as a result of events inside of a cell, such as apoptosis or autophagy. PCD is carried out in a biological process, which usually confers ...
* Limitless number of cell divisions * Promoting blood vessel construction *
Invasion An invasion is a Offensive (military), military offensive in which large numbers of combatants of one geopolitics, geopolitical Legal entity, entity aggressively enter territory (country subdivision), territory owned by another such entity, gen ...
of tissue and formation of
metastases Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then ...
The progression from normal cells to cells that can form a detectable mass to outright cancer involves multiple steps known as malignant progression.


Signs and symptoms

When cancer begins, it produces no symptoms. Signs and symptoms appear as the mass grows or ulcerates. The findings that result depend on cancer's type and location. Few symptoms are
specific Specific may refer to: * Specificity (disambiguation) * Specific, a cure or therapy for a specific illness Law * Specific deterrence, focussed on an individual * Specific finding, intermediate verdict used by a jury in determining the fina ...
. Many frequently occur in individuals who have other conditions. Cancer can be difficult to diagnose and can be considered a " great imitator." People may become anxious or depressed post-diagnosis. The risk of suicide in people with cancer is approximately double.


Local symptoms

Local symptoms may occur due to the mass of the tumor or its ulceration. For example, mass effects from lung cancer can block the
bronchus A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchu ...
resulting in cough or
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...
; esophageal cancer can cause narrowing of the
esophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
, making it difficult or painful to swallow; and colorectal cancer may lead to narrowing or blockages in the
bowel The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
, affecting bowel habits. Masses in breasts or testicles may produce observable lumps.
Ulceration An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...
can cause bleeding that can lead to symptoms such as coughing up blood (lung cancer),
anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, t ...
or rectal bleeding (colon cancer),
blood in the urine Hematuria or haematuria is defined as the presence of blood or red blood cells in the urine. “Gross hematuria” occurs when urine appears red, brown, or tea-colored due to the presence of blood. Hematuria may also be subtle and only detectable w ...
(bladder cancer), or
abnormal vaginal bleeding Vaginal bleeding is any expulsion of blood from the vagina. This bleeding may originate from the uterus, vaginal wall, or cervix. Generally, it is either part of a normal menstrual cycle or is caused by hormonal or other problems of the reprod ...
(endometrial or cervical cancer). Although localized pain may occur in advanced cancer, the initial tumor is usually painless. Some cancers can cause a buildup of fluid within the chest or
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
.Holland Chp. 1


Systemic symptoms

Systemic symptoms may occur due to the body's response to the cancer. This may include fatigue, unintentional weight loss, or skin changes. Some cancers can cause a systemic inflammatory state that leads to ongoing muscle loss and weakness, known as
cachexia Cachexia () is a complex syndrome associated with an underlying illness, causing ongoing muscle loss that is not entirely reversed with nutritional supplementation. A range of diseases can cause cachexia, most commonly cancer, congestive heart ...
. Some cancers, such as Hodgkin's disease,
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
s, and
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
or
kidney cancer Kidney cancer, also known as renal cancer, is a group of cancers that starts in the kidney. Symptoms may include blood in the urine, lump in the abdomen, or back pain. Fever, weight loss, and tiredness may also occur. Complications can include sp ...
s, can cause a persistent
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
. Some systemic symptoms of cancer are caused by hormones or other molecules produced by the tumor, known as
paraneoplastic syndromes A paraneoplastic syndrome is a syndrome (a set of signs and symptoms) that is the consequence of a tumor in the body (usually a cancerous one), specifically due to the production of chemical signaling molecules (such as hormones or cytokines) by ...
. Common paraneoplastic syndromes include hypercalcemia, which can cause altered mental state, constipation and dehydration, or
hyponatremia Hyponatremia or hyponatraemia is a low concentration of sodium in the blood. It is generally defined as a sodium concentration of less than 135  mmol/L (135  mEq/L), with severe hyponatremia being below 120 mEq/L. Symptoms can be a ...
, which can also cause altered mental status, vomiting, headaches, or seizures.


Metastasis

Metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then ...
is the spread of cancer to other locations in the body. The dispersed tumors are called metastatic tumors, while the original is called the primary tumor. Almost all cancers can metastasize. Most cancer deaths are due to cancer that has metastasized. Metastasis is common in the late stages of cancer and it can occur via the blood or the lymphatic system or both. The typical steps in metastasis are local
invasion An invasion is a Offensive (military), military offensive in which large numbers of combatants of one geopolitics, geopolitical Legal entity, entity aggressively enter territory (country subdivision), territory owned by another such entity, gen ...
,
intravasation Intravasation is the invasion of cancer cells through the basement membrane into a blood or lymphatic vessel. Intravasation is one of several carcinogenic events that initiate the escape of cancerous cells from their primary sites. Other mechanisms ...
into the blood or lymph, circulation through the body,
extravasation __NOTOC__ Extravasation is the leakage of a fluid out of its container into the surrounding area, especially blood or blood cells from vessels. In the case of inflammation, it refers to the movement of white blood cells from the capillaries to th ...
into the new tissue, proliferation and angiogenesis. Different types of cancers tend to metastasize to particular organs, but overall the most common places for metastases to occur are the lungs,
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
, brain, and the
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
s.


Causes

The majority of cancers, some 90–95% of cases, are due to genetic mutations from environmental and lifestyle factors. The remaining 5–10% are due to inherited genetics. ''
Environmental A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
'' refers to any cause that is not inherited, such as lifestyle, economic, and behavioral factors and not merely pollution. Common environmental factors that contribute to cancer death include tobacco use (25–30%), diet and
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
(30–35%), infections (15–20%), radiation (both ionizing and non-ionizing, up to 10%), lack of
physical activity Physical activity is defined as any voluntary bodily movement produced by skeletal muscles that requires energy expenditure.Global Recommendations on Physical Activity for Health, 2009. World Health Organization. Geneva, Switzerland. Accessed 13/ ...
, and pollution. Psychological stress does not appear to be a risk factor for the onset of cancer, though it may worsen outcomes in those who already have cancer. It is not generally possible to prove what caused a particular cancer because the various causes do not have specific fingerprints. For example, if a person who uses tobacco heavily develops lung cancer, then it was probably caused by the tobacco use, but since everyone has a small chance of developing lung cancer as a result of air pollution or radiation, the cancer may have developed for one of those reasons. Excepting the rare transmissions that occur with pregnancies and occasional
organ donors Organ donation is the process when a person allows an organ of their own to be removed and transplanted to another person, legally, either by consent while the donor is alive or dead with the assent of the next of kin. Donation may be for re ...
, cancer is generally not a
transmissible disease In medicine, public health, and biology, transmission is the passing of a pathogen causing communicable disease from an infected host individual or group to a particular individual or group, regardless of whether the other individual was previou ...
, however factors that may have contributed to the development of cancer can be transmissible; such as oncoviruses like
hepatitis B Hepatitis B is an infectious disease caused by the '' Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. ...
, Epstein-Barr virus and HIV.


Chemicals

Exposure to particular substances have been linked to specific types of cancer. These substances are called ''
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
s''.
Tobacco smoke Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C d ...
, for example, causes 90% of lung cancer. It also causes cancer in the larynx, head, neck, stomach, bladder, kidney,
esophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
and
pancreas The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an en ...
. Tobacco smoke contains over fifty known carcinogens, including nitrosamines and
polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s. Tobacco is responsible for about one in five cancer deaths worldwide and about one in three in the developed world. Lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking rates since the 1950s followed by decreases in lung cancer death rates in men since 1990. In Western Europe, 10% of cancers in males and 3% of cancers in females are attributed to alcohol exposure, especially liver and digestive tract cancers. Cancer from work-related substance exposures may cause between 2 and 20% of cases, causing at least 200,000 deaths. Cancers such as lung cancer and
mesothelioma Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs (known as the mesothelium). The most common area affected is the lining of the lungs and chest wall. Less commonly the lining ...
can come from inhaling tobacco smoke or asbestos fibers, or
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
from exposure to
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
. Exposure to
perfluorooctanoic acid Perfluorooctanoic acid (PFOA; conjugate base perfluorooctanoate; also known colloquially as C8, for its 8 carbon chain structure) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes a ...
(PFOA), which is predominantly used in the production of
Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemo ...
, is known to cause two kinds of cancer.


Diet and exercise

Diet,
physical inactivity Physical inactivity refers to the lack of moderate-to-vigorous physical activity in a person's lifestyle. It is distinct from sedentary behavior. Health effects The World Health Organization (WHO) has defined physical inactivity as a global public ...
, and
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
are related to up to 30–35% of cancer deaths. In the United States, excess body weight is associated with the development of many types of cancer and is a factor in 14–20% of cancer deaths. A UK study including data on over 5 million people showed higher body mass index to be related to at least 10 types of cancer and responsible for around 12,000 cases each year in that country. Physical inactivity is believed to contribute to cancer risk, not only through its effect on body weight but also through negative effects on the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...
and
endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
. More than half of the effect from the diet is due to
overnutrition Overnutrition (also known as hyperalimentation) is a form of malnutrition in which the intake of nutrients is oversupplied. The amount of nutrients exceeds the amount required for normal growth, development, and metabolism. The term can also ref ...
(eating too much), rather than from eating too few vegetables or other healthful foods. Some specific foods are linked to specific cancers. A high-salt diet is linked to
gastric cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...
.
Aflatoxin B1 Aflatoxin B1 is an aflatoxin produced by '' Aspergillus flavus'' and '' A. parasiticus''. It is a very potent carcinogen with a TD50 3.2 μg/kg/day in rats. This carcinogenic potency varies across species with some, such as rats and monkeys, see ...
, a frequent food contaminant, causes liver cancer.
Betel nut The betel (''Piper betle'') is a vine of the family Piperaceae, which includes pepper and kava. The betel plant is native to Southeast Asia. It is an evergreen, dioecious perennial, with glossy heart-shaped leaves and white catkins. Betel p ...
chewing can cause oral cancer. National differences in dietary practices may partly explain differences in cancer incidence. For example,
gastric cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...
is more common in Japan due to its high-salt diet while colon cancer is more common in the United States. Immigrant cancer profiles mirror those of their new country, often within one generation.


Infection

Worldwide approximately 18% of cancer deaths are related to
infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
s. This proportion ranges from a high of 25% in Africa to less than 10% in the developed world. Viruses are the usual infectious agents that cause cancer but cancer bacteria and
parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
may also play a role. Oncoviruses (viruses that can cause cancer) include
human papillomavirus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and res ...
( cervical cancer),
Epstein–Barr virus The Epstein–Barr virus (EBV), formally called ''Human gammaherpesvirus 4'', is one of the nine known human herpesvirus types in the herpes family, and is one of the most common viruses in humans. EBV is a double-stranded DNA virus. It is b ...
( B-cell lymphoproliferative disease and
nasopharyngeal carcinoma Nasopharyngeal carcinoma (NPC), or nasopharynx cancer, is the most common cancer originating in the nasopharynx, most commonly in the postero-lateral nasopharynx or pharyngeal recess ( fossa of Rosenmüller), accounting for 50% of cases. NPC occurs ...
),
Kaposi's sarcoma herpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) is the ninth known human herpesvirus; its formal name according to the International Committee on Taxonomy of Viruses (ICTV) is ''Human gammaherpesvirus 8'', or HHV-8 in short. Like other herpesvirus ...
(
Kaposi's sarcoma Kaposi's sarcoma (KS) is a type of cancer that can form masses in the skin, in lymph nodes, in the mouth, or in other organs. The skin lesions are usually painless, purple and may be flat or raised. Lesions can occur singly, multiply in a limit ...
and primary effusion lymphomas),
hepatitis B Hepatitis B is an infectious disease caused by the '' Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. ...
and hepatitis C viruses ( hepatocellular carcinoma) and human T-cell leukemia virus-1 (T-cell leukemias). Bacterial infection may also increase the risk of cancer, as seen in ''
Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is thoug ...
''-induced
gastric carcinoma Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lym ...
. Parasitic infections associated with cancer include ''
Schistosoma haematobium ''Schistosoma haematobium'' (urinary blood fluke) is a species of digenetic trematode, belonging to a group (genus) of blood flukes (''Schistosoma''). It is found in Africa and the Middle East. It is the major agent of schistosomiasis, the most ...
'' ( squamous cell carcinoma of the bladder) and the
liver fluke Liver fluke is a collective name of a polyphyletic group of parasitic trematodes under the phylum Platyhelminthes. They are principally parasites of the liver of various mammals, including humans. Capable of moving along the blood circulation, t ...
s, ''
Opisthorchis viverrini ''Opisthorchis viverrini'', common name Southeast Asian liver fluke, is a food-borne trematode parasite from the family Opisthorchiidae that infects the bile duct. People are infected after eating raw or undercooked fish. Infection with the par ...
'' and ''
Clonorchis sinensis ''Clonorchis sinensis'', the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding o ...
'' ( cholangiocarcinoma).


Radiation

Radiation exposure such as
ultraviolet radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
and radioactive material is a risk factor for cancer. Many
non-melanoma skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC ...
s are due to ultraviolet radiation, mostly from sunlight. Sources of ionizing radiation include medical imaging and
radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
gas. Ionizing radiation is not a particularly strong mutagen. Residential exposure to
radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
gas, for example, has similar cancer risks as
passive smoking Passive smoking is the inhalation of tobacco smoke, called secondhand smoke (SHS), or environmental tobacco smoke (ETS), by persons other than the intended "active" smoker. It occurs when tobacco smoke enters an environment, causing its inhalat ...
. Radiation is a more potent source of cancer when combined with other cancer-causing agents, such as radon plus tobacco smoke. Radiation can cause cancer in most parts of the body, in all animals and at any age. Children are twice as likely to develop radiation-induced leukemia as adults; radiation exposure before birth has ten times the effect. Medical use of ionizing radiation is a small but growing source of radiation-induced cancers. Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer. It is also used in some kinds of medical imaging. Prolonged exposure to
ultraviolet radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
from the
sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
can lead to melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave
UVB Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
, as the cause of most non-melanoma
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
s, which are the most common forms of cancer in the world. Non-ionizing
radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...
radiation from mobile phones, electric power transmission and other similar sources has been described as a possible carcinogen by the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
's
International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...
. Evidence, however, has not supported a concern. This includes that studies have not found a consistent link between mobile phone radiation and cancer risk.


Heredity

The vast majority of cancers are non-hereditary (sporadic).
Hereditary cancer A cancer syndrome, or family cancer syndrome, is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Ca ...
s are primarily caused by an inherited genetic defect. Less than 0.3% of the population are carriers of a genetic mutation that has a large effect on cancer risk and these cause less than 3–10% of cancer. Some of these
syndrome A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek language, Greek σύνδρομον, meaning "concurrence". When a sy ...
s include: certain inherited mutations in the genes ''
BRCA1 Breast cancer type 1 susceptibility protein is a protein that in humans is encoded by the ''BRCA1'' () gene. Orthologs are common in other vertebrate species, whereas invertebrate genomes may encode a more distantly related gene. ''BRCA1'' is a ...
'' and '' BRCA2'' with a more than 75% risk of breast cancer and
ovarian cancer Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...
, and
hereditary nonpolyposis colorectal cancer Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome is an autosomal dominant genetic condition that is associated with a high risk of colon cancer as well as other cancers including endometrial cancer (second most common), ovary, ...
(HNPCC or Lynch syndrome), which is present in about 3% of people with colorectal cancer, among others. Statistically for cancers causing most mortality, the relative risk of developing colorectal cancer when a
first-degree relative A first-degree relative (FDR) is a person's parent (father or mother), full sibling (brother or sister) or child. It constitutes a category of family members that largely overlaps with the term nuclear family, but without spouses. If the persons ...
(parent, sibling or child) has been diagnosed with it is about 2. The corresponding relative risk is 1.5 for lung cancer, and 1.9 for prostate cancer. For breast cancer, the relative risk is 1.8 with a first-degree relative having developed it at 50 years of age or older, and 3.3 when the relative developed it when being younger than 50 years of age. Taller people have an increased risk of cancer because they have more cells than shorter people. Since height is genetically determined to a large extent, taller people have a heritable increase of cancer risk.


Physical agents

Some substances cause cancer primarily through their physical, rather than chemical, effects. A prominent example of this is prolonged exposure to asbestos, naturally occurring mineral fibers that are a major cause of
mesothelioma Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs (known as the mesothelium). The most common area affected is the lining of the lungs and chest wall. Less commonly the lining ...
(cancer of the
serous membrane The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...
) usually the serous membrane surrounding the lungs. Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers, such as
wollastonite Wollastonite is a calcium inosilicate mineral ( Ca Si O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature ...
,
attapulgite Palygorskite or attapulgite is a magnesium aluminium phyllosilicate with the chemical formula ) that occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth. Some smaller deposits of ...
, glass wool and
rock wool Mineral wool is any fibrous material formed by spinning or drawing molten mineral or rock materials such as slag and ceramics. Applications of mineral wool include thermal insulation (as both structural insulation and pipe insulation), filt ...
, are believed to have similar effects. Non-fibrous particulate materials that cause cancer include powdered metallic
cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...
and
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
and
crystalline silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
(
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
,
cristobalite Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the ...
and
tridymite Tridymite is a high-temperature polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is Si O2. Tridymite was first describe ...
). Usually, physical carcinogens must get inside the body (such as through inhalation) and require years of exposure to produce cancer. Physical trauma resulting in cancer is relatively rare. Claims that breaking bones resulted in bone cancer, for example, have not been proven. Similarly, physical trauma is not accepted as a cause for cervical cancer, breast cancer or brain cancer. One accepted source is frequent, long-term application of hot objects to the body. It is possible that repeated burns on the same part of the body, such as those produced by
kanger A kanger (; also known as kangri or kangid or kangir) is an earthen pot woven around with wicker filled with hot embers used by Kashmiris beneath their traditional clothing pheran to keep the chill at bay, which is also regarded as a work of art. ...
and kairo heaters (charcoal
hand warmer Hand warmers are small (mostly disposable) packets which are held in the hand and produce heat on demand to warm cold hands. They are commonly used in outdoor activities. Other types of warmers are available to provide soothing heat for muscular ...
s), may produce skin cancer, especially if carcinogenic chemicals are also present. Frequent consumption of scalding hot tea may produce esophageal cancer. Generally, it is believed that cancer arises, or a pre-existing cancer is encouraged, during the process of healing, rather than directly by the trauma. However, repeated injuries to the same tissues might promote excessive cell proliferation, which could then increase the odds of a cancerous mutation. Chronic
inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...
has been hypothesized to directly cause mutation. Inflammation can contribute to proliferation, survival, angiogenesis and migration of cancer cells by influencing the
tumor microenvironment The tumor microenvironment (TME) is the environment around a tumor, including the surrounding blood vessels, immune cells, fibroblasts, signaling molecules and the extracellular matrix (ECM). The tumor and the surrounding microenvironment are ...
.
Oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.
s build up an inflammatory pro-tumorigenic microenvironment.


Hormones

Some
hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are require ...
s play a role in the development of cancer by promoting cell proliferation.
Insulin-like growth factor The insulin-like growth factors (IGFs) are proteins with high sequence similarity to insulin. IGFs are part of a complex system that cells use to communicate with their physiologic environment. This complex system (often referred to as the IGF " ...
s and their binding proteins play a key role in cancer cell proliferation, differentiation and apoptosis, suggesting possible involvement in carcinogenesis. Hormones are important agents in sex-related cancers, such as cancer of the breast, endometrium, prostate, ovary and
testis A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...
and also of
thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck. C ...
and
bone cancer A bone tumor is an abnormal growth of tissue in bone, traditionally classified as noncancerous (benign) or cancerous (malignant). Cancerous bone tumors usually originate from a cancer in another part of the body such as from lung, breast, thy ...
. For example, the daughters of women who have breast cancer have significantly higher levels of
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...
and progesterone than the daughters of women without breast cancer. These higher hormone levels may explain their higher risk of breast cancer, even in the absence of a breast-cancer gene. Similarly, men of African ancestry have significantly higher levels of
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristi ...
than men of European ancestry and have a correspondingly higher level of prostate cancer. Men of Asian ancestry, with the lowest levels of testosterone-activating
androstanediol glucuronide 3α-Androstanediol glucuronide (3α-ADG) is a metabolite formed from human androgens; compounds involved in the development and maintenance of sexual characteristics. It is formed by the glucuronidation of both dihydrotestosterone and testosterone ...
, have the lowest levels of prostate cancer. Other factors are relevant: obese people have higher levels of some hormones associated with cancer and a higher rate of those cancers. Women who take
hormone replacement therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. These symptoms can include hot flashes, vaginal ...
have a higher risk of developing cancers associated with those hormones. On the other hand, people who exercise far more than average have lower levels of these hormones and lower risk of cancer.
Osteosarcoma An osteosarcoma (OS) or osteogenic sarcoma (OGS) (or simply bone cancer) is a cancerous tumor in a bone. Specifically, it is an aggressive malignant neoplasm that arises from primitive transformed cells of mesenchymal origin (and thus a sarcoma ...
may be promoted by
growth hormone Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in h ...
s. Some treatments and prevention approaches leverage this cause by artificially reducing hormone levels and thus discouraging hormone-sensitive cancers.


Autoimmune diseases

There is an association between
celiac disease Coeliac disease (British English) or celiac disease (American English) is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barle ...
and an increased risk of all cancers. People with untreated celiac disease have a higher risk, but this risk decreases with time after diagnosis and strict treatment, probably due to the adoption of a
gluten-free diet A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats. The incl ...
, which seems to have a protective role against development of malignancy in people with celiac disease. However, the delay in diagnosis and initiation of a gluten-free diet seems to increase the risk of malignancies. Rates of gastrointestinal cancers are increased in people with Crohn's disease and
ulcerative colitis Ulcerative colitis (UC) is a long-term condition that results in inflammation and ulcers of the colon and rectum. The primary symptoms of active disease are abdominal pain and diarrhea mixed with blood (hematochezia). Weight loss, fever, and ...
, due to chronic inflammation. Also,
immunomodulators Immunotherapy or biological therapy is the treatment of disease by activating or suppressing the immune system. Immunotherapies designed to elicit or amplify an immune response are classified as ''activation immunotherapies,'' while immunotherap ...
and biologic agents used to treat these diseases may promote developing extra-intestinal malignancies.


Pathophysiology


Genetics

Cancer is fundamentally a disease of tissue growth regulation. For a normal cell to
transform Transform may refer to: Arts and entertainment * Transform (scratch), a type of scratch used by turntablists * ''Transform'' (Alva Noto album), 2001 * ''Transform'' (Howard Jones album) or the title song, 2019 * ''Transform'' (Powerman 5000 album ...
into a cancer cell, the
gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s that regulate cell growth and differentiation must be altered. The affected genes are divided into two broad categories.
Oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.
s are genes that promote cell growth and reproduction.
Tumor suppressor gene A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a cell during cell division and replication. If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated, it results in a loss or re ...
s are genes that inhibit cell division and survival. Malignant transformation can occur through the formation of novel oncogenes, the inappropriate over-expression of normal oncogenes, or by the under-expression or disabling of tumor suppressor genes. Typically, changes in multiple genes are required to transform a normal cell into a cancer cell. Genetic changes can occur at different levels and by different mechanisms. The gain or loss of an entire
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
can occur through errors in mitosis. More common are
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
s, which are changes in the
nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...
sequence of genomic DNA. Large-scale mutations involve the deletion or gain of a portion of a chromosome. Genomic amplification occurs when a cell gains copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material. Translocation occurs when two separate chromosomal regions become abnormally fused, often at a characteristic location. A well-known example of this is the
Philadelphia chromosome The Philadelphia chromosome or Philadelphia translocation (Ph) is a specific genetic abnormality in chromosome 22 of leukemia cancer cells (particularly chronic myeloid leukemia (CML) cells). This chromosome is defective and unusually short becaus ...
, or translocation of chromosomes 9 and 22, which occurs in chronic myelogenous leukemia and results in production of the BCR- abl fusion protein, an oncogenic
tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...
. Small-scale mutations include point mutations, deletions, and insertions, which may occur in the promoter region of a gene and affect its
expression Expression may refer to: Linguistics * Expression (linguistics), a word, phrase, or sentence * Fixed expression, a form of words with a specific meaning * Idiom, a type of fixed expression * Metaphorical expression, a particular word, phrase, o ...
, or may occur in the gene's
coding sequence The coding region of a gene, also known as the coding sequence (CDS), is the portion of a gene's DNA or RNA that codes for protein. Studying the length, composition, regulation, splicing, structures, and functions of coding regions compared to n ...
and alter the function or stability of its
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
product. Disruption of a single gene may also result from integration of genomic material from a
DNA virus A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and ...
or retrovirus, leading to the expression of ''viral'' oncogenes in the affected cell and its descendants. Replication of the data contained within the DNA of living cells will probabilistically result in some errors (mutations). Complex error correction and prevention are built into the process and safeguard the cell against cancer. If a significant error occurs, the damaged cell can self-destruct through programmed cell death, termed apoptosis. If the error control processes fail, then the mutations will survive and be passed along to daughter cells. Some environments make errors more likely to arise and propagate. Such environments can include the presence of disruptive substances called
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
s, repeated physical injury, heat, ionising radiation, or hypoxia. The errors that cause cancer are self-amplifying and compounding, for example: * A mutation in the error-correcting machinery of a cell might cause that cell and its children to accumulate errors more rapidly. * A further mutation in an oncogene might cause the cell to reproduce more rapidly and more frequently than its normal counterparts. * A further mutation may cause loss of a tumor suppressor gene, disrupting the apoptosis signaling pathway and immortalizing the cell. * A further mutation in the signaling machinery of the cell might send error-causing signals to nearby cells. The transformation of a normal cell into cancer is akin to a
chain reaction A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events. Chain reactions are one way that sys ...
caused by initial errors, which compound into more severe errors, each progressively allowing the cell to escape more controls that limit normal tissue growth. This rebellion-like scenario is an undesirable survival of the fittest, where the driving forces of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
work against the body's design and enforcement of order. Once cancer has begun to develop, this ongoing process, termed '' clonal evolution'', drives progression towards more invasive
stages Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * S ...
. Clonal evolution leads to intra-
tumour heterogeneity A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
(cancer cells with heterogeneous mutations) that complicates designing effective treatment strategies and requires an evolutionary approach to designing treatment. Characteristic abilities developed by cancers are divided into categories, specifically evasion of apoptosis, self-sufficiency in growth signals, insensitivity to anti-growth signals, sustained angiogenesis, limitless replicative potential, metastasis, reprogramming of energy metabolism and evasion of immune destruction.


Epigenetics

The classical view of cancer is a set of diseases driven by progressive genetic abnormalities that include mutations in tumor-suppressor genes and
oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.
s, and in
chromosomal A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
abnormalities. A role for epigenetic alterations was identified in the early 21st century. Epigenetic alterations are functionally relevant modifications to the genome that do not change the nucleotide sequence. Examples of such modifications are changes in DNA methylation (hypermethylation and hypomethylation),
histone modification In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn are w ...
and changes in chromosomal architecture (caused by inappropriate expression of proteins such as
HMGA2 High-mobility group AT-hook 2, also known as HMGA2, is a protein that, in humans, is encoded by the ''HMGA2'' gene. Function This gene encodes a protein that belongs to the non-histone chromosomal high-mobility group (HMG) protein family. HMG ...
or
HMGA1 High-mobility group protein HMG-I/HMG-Y is a protein that in humans is encoded by the ''HMGA1'' gene. Function This gene encodes a non-histone chromatin protein involved in many cellular processes, including regulation of inducible gene transc ...
). Each of these alterations regulates gene expression without altering the underlying DNA sequence. These changes may remain through
cell division Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there ar ...
s, endure for multiple generations, and can be considered as equivalent to mutations. Epigenetic alterations occur frequently in cancers. As an example, one study listed protein coding genes that were frequently altered in their methylation in association with colon cancer. These included 147 hypermethylated and 27 hypomethylated genes. Of the hypermethylated genes, 10 were hypermethylated in 100% of colon cancers and many others were hypermethylated in more than 50% of colon cancers. While epigenetic alterations are found in cancers, the epigenetic alterations in DNA repair genes, causing reduced expression of DNA repair proteins, may be of particular importance. Such alterations may occur early in progression to cancer and are a possible cause of the genetic instability characteristic of cancers. Reduced expression of DNA repair genes disrupts DNA repair. This is shown in the figure at the 4th level from the top. (In the figure, red wording indicates the central role of DNA damage and defects in DNA repair in progression to cancer.) When DNA repair is deficient DNA damage remains in cells at a higher than usual level (5th level) and causes increased frequencies of mutation and/or epimutation (6th level). Mutation rates increase substantially in cells defective in
DNA mismatch repair DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage. Mismatch ...
or in
homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
al repair (HRR). Chromosomal rearrangements and aneuploidy also increase in HRR defective cells. Higher levels of DNA damage cause increased mutation (right side of figure) and increased epimutation. During repair of DNA double strand breaks, or repair of other DNA damage, incompletely cleared repair sites can cause epigenetic gene silencing. Deficient expression of DNA repair proteins due to an inherited mutation can increase cancer risks. Individuals with an inherited impairment in any of 34 DNA repair genes (see article
DNA repair-deficiency disorder A DNA repair-deficiency disorder is a medical condition due to reduced functionality of DNA repair. DNA repair defects can cause an accelerated aging disease or an increased risk of cancer, or sometimes both. DNA repair defects and accelerated a ...
) have increased cancer risk, with some defects ensuring a 100% lifetime chance of cancer (e.g. p53 mutations). Germ line DNA repair mutations are noted on the figure's left side. However, such germline mutations (which cause highly penetrant cancer syndromes) are the cause of only about 1 percent of cancers. In sporadic cancers, deficiencies in DNA repair are occasionally caused by a mutation in a DNA repair gene but are much more frequently caused by epigenetic alterations that reduce or silence expression of DNA repair genes. This is indicated in the figure at the 3rd level. Many studies of heavy metal-induced carcinogenesis show that such heavy metals cause a reduction in expression of DNA repair enzymes, some through epigenetic mechanisms. DNA repair inhibition is proposed to be a predominant mechanism in heavy metal-induced carcinogenicity. In addition, frequent epigenetic alterations of the DNA sequences code for small RNAs called
microRNA MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. mi ...
s (or miRNAs). miRNAs do not code for proteins, but can "target" protein-coding genes and reduce their expression. Cancers usually arise from an assemblage of mutations and epimutations that confer a selective advantage leading to clonal expansion (see Field defects in progression to cancer). Mutations, however, may not be as frequent in cancers as epigenetic alterations. An average cancer of the breast or colon can have about 60 to 70 protein-altering mutations, of which about three or four may be "driver" mutations and the remaining ones may be "passenger" mutations.


Metastasis

Metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then ...
is the spread of cancer to other locations in the body. The dispersed tumors are called metastatic tumors, while the original is called the primary tumor. Almost all cancers can metastasize. Most cancer deaths are due to cancer that has metastasized. Metastasis is common in the late stages of cancer and it can occur via the blood or the lymphatic system or both. The typical steps in metastasis are local
invasion An invasion is a Offensive (military), military offensive in which large numbers of combatants of one geopolitics, geopolitical Legal entity, entity aggressively enter territory (country subdivision), territory owned by another such entity, gen ...
,
intravasation Intravasation is the invasion of cancer cells through the basement membrane into a blood or lymphatic vessel. Intravasation is one of several carcinogenic events that initiate the escape of cancerous cells from their primary sites. Other mechanisms ...
into the blood or lymph, circulation through the body,
extravasation __NOTOC__ Extravasation is the leakage of a fluid out of its container into the surrounding area, especially blood or blood cells from vessels. In the case of inflammation, it refers to the movement of white blood cells from the capillaries to th ...
into the new tissue, proliferation and angiogenesis. Different types of cancers tend to metastasize to particular organs, but overall the most common places for metastases to occur are the lungs,
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
, brain and the
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
s.


Metabolism

Normal cells typically generate only about 30% of energy from glycolysis, whereas most cancers rely on glycolysis for energy production ( Warburg effect). But a minority of cancer types rely on oxidative phosphorylation as the primary energy source, including
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
,
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
, and endometrial cancer. Even in these cases, however, the use of glycolysis as an energy source rarely exceeds 60%. A few cancers use
glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...
as the major energy source, partly because it provides nitrogen required for
nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...
(DNA, RNA) synthesis. Cancer stem cells often use oxidative phosphorylation or glutamine as a primary energy source. Several studies have indicated that the enzyme
sirtuin 6 Sirtuin 6 (SIRT6 or Sirt6) is a stress responsive protein deacetylase and mono-ADP ribosyltransferase enzyme encoded by the SIRT6 gene. In laboratory research, SIRT6 appears to function in multiple molecular pathways related to aging, including ...
is selectively inactivated during
oncogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abno ...
in a variety of tumor types by inducing glycolysis. Another
sirtuin Sirtuins are a family of signaling proteins involved in metabolic regulation. They are ancient in animal evolution and appear to possess a highly conserved structure throughout all kingdoms of life. Chemically, sirtuins are a class of proteins t ...
,
sirtuin 3 NAD-dependent deacetylase sirtuin-3, mitochondrial also known as SIRT3 is a protein that in humans is encoded by the ''SIRT3'' gene irtuin (silent mating type information regulation 2 homolog) 3 (S. cerevisiae) SIRT3 is member of the mammalian sir ...
inhibits cancers that depend upon glycolysis, but promotes cancers that depend upon oxidative phosphorylation. A
low-carbohydrate diet Low-carbohydrate diets restrict carbohydrate consumption relative to the average diet. Foods high in carbohydrates (e.g., sugar, bread, pasta) are limited, and replaced with foods containing a higher percentage of fat and protein (e.g., meat, ...
(
ketogenic diet The ketogenic diet is a high- fat, adequate-protein, low-carbohydrate dietary therapy that in conventional medicine is used mainly to treat hard-to-control (refractory) epilepsy in children. The diet forces the body to burn fats rather than ca ...
) has sometimes been recommended as a supportive therapy for cancer treatment.


Diagnosis

Most cancers are initially recognized either because of the appearance of signs or symptoms or through
screening Screening may refer to: * Screening cultures, a type a medical test that is done to find an infection * Screening (economics), a strategy of combating adverse selection (includes sorting resumes to select employees) * Screening (environmental), a ...
. Neither of these leads to a definitive diagnosis, which requires the examination of a tissue sample by a
pathologist Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in t ...
. People with suspected cancer are investigated with
medical test A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
s. These commonly include blood tests,
X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10 nanometers, corresponding to frequencies in the range 30&nbs ...
, ( contrast) CT scans and
endoscopy An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are inse ...
. The tissue
diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...
from the biopsy indicates the type of cell that is proliferating, its
histological grade In pathology, grading is a measure of the cell appearance in tumors and other neoplasms. Some pathology grading systems apply only to malignant neoplasms (cancer); others apply also to benign neoplasms. The neoplastic grading is a measure of cell ...
, genetic abnormalities and other features. Together, this information is useful to evaluate the prognosis and to choose the best treatment.
Cytogenetics Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis an ...
and immunohistochemistry are other types of tissue tests. These tests provide information about molecular changes (such as
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
s,
fusion gene A fusion gene is a hybrid gene formed from two previously independent genes. It can occur as a result of translocation, interstitial deletion, or chromosomal inversion. Fusion genes have been found to be prevalent in all main types of human neopla ...
s and numerical
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
changes) and may thus also indicate the prognosis and best treatment. Cancer diagnosis can cause psychological distress and psychosocial interventions, such as talking therapy, may help people with this.


Classification

Cancers are classified by the type of cell that the tumor cells resemble and is therefore presumed to be the origin of the tumor. These types include: * Carcinoma: Cancers derived from
epithelial Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercell ...
cells. This group includes many of the most common cancers and include nearly all those in the
breast The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and sec ...
,
prostate The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and phys ...
, lung,
pancreas The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an en ...
and colon. *
Sarcoma A sarcoma is a malignant tumor, a type of cancer that arises from transformed cells of mesenchymal ( connective tissue) origin. Connective tissue is a broad term that includes bone, cartilage, fat, vascular, or hematopoietic tissues, and sar ...
: Cancers arising from connective tissue (i.e.
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
, cartilage, fat, nerve), each of which develops from cells originating in
mesenchymal Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...
cells outside the bone marrow. *
Lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
and
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
: These two classes arise from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. * Germ cell tumor: Cancers derived from
pluripotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
cells, most often presenting in the
testicle A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoste ...
or the ovary (
seminoma A seminoma is a germ cell tumor of the testicle or, more rarely, the mediastinum or other extra-gonadal locations. It is a malignant neoplasm and is one of the most treatable and curable cancers, with a survival rate above 95% if discovered in ...
and
dysgerminoma A dysgerminoma is a type of germ cell tumor; it usually is malignant and usually occurs in the ovary. A tumor of the identical histology but not occurring in the ovary may be described by an alternate name: seminoma in the testis or germinoma ...
, respectively). *
Blastoma A blastoma is a type of cancer, more common in children, that is caused by malignancies in precursor cells, often called blasts. Examples are nephroblastoma, medulloblastoma, and retinoblastoma. The suffix ''-blastoma'' is used to imply a tumor ...
: Cancers derived from immature "precursor" cells or embryonic tissue. Cancers are usually named using ''-carcinoma'', ''-sarcoma'' or ''-blastoma'' as a suffix, with the Latin or Greek word for the organ or tissue of origin as the root. For example, cancers of the liver parenchyma arising from malignant epithelial cells is called '' hepatocarcinoma'', while a malignancy arising from primitive liver precursor cells is called a
hepatoblastoma Hepatoblastoma is a malignant liver cancer occurring in infants and children and composed of tissue resembling fetal liver cells, mature liver cells, or bile duct cells. They usually present with an abdominal mass. The disease is most commonly di ...
and a cancer arising from fat cells is called a ''
liposarcoma Liposarcomas are the most common subtype of soft tissue sarcomas, accounting for at least 20% of all sarcomas in adults. Soft tissue sarcomas are rare neoplasms with over 150 different histological subtypes or forms. Liposarcomas arise from the pr ...
''. For some common cancers, the English organ name is used. For example, the most common type of breast cancer is called '' ductal carcinoma of the breast''. Here, the adjective ''ductal'' refers to the appearance of cancer under the microscope, which suggests that it has originated in the milk ducts.
Benign tumor A benign tumor is a mass of cells (tumor) that does not invade neighboring tissue or metastasize (spread throughout the body). Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have re ...
s (which are not cancers) are named using ''-oma'' as a suffix with the organ name as the root. For example, a benign tumor of smooth muscle cells is called a '' leiomyoma'' (the common name of this frequently occurring benign tumor in the uterus is '' fibroid''). Confusingly, some types of cancer use the ''-noma'' suffix, examples including melanoma and
seminoma A seminoma is a germ cell tumor of the testicle or, more rarely, the mediastinum or other extra-gonadal locations. It is a malignant neoplasm and is one of the most treatable and curable cancers, with a survival rate above 95% if discovered in ...
. Some types of cancer are named for the size and shape of the cells under a microscope, such as giant cell carcinoma, spindle cell carcinoma and
small-cell carcinoma Small-cell carcinoma is a type of highly malignant cancer that most commonly arises within the lung, although it can occasionally arise in other body sites, such as the cervix, prostate, and gastrointestinal tract. Compared to non-small cell car ...
. File:Breast cancer gross appearance.jpg, An invasive
ductal carcinoma Ductal carcinoma is a type of tumor that primarily presents in the ducts of a gland. Types include: * Mammary **Ductal carcinoma in situ **Invasive ductal carcinoma * Pancreatic ductal carcinoma Pancreatic cancer arises when cells in the p ...
of the breast (pale area at the center) surrounded by spikes of whitish scar tissue and yellow fatty tissue File:Colon cancer 2.jpg, An invasive
colorectal carcinoma Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...
(top center) in a
colectomy Colectomy ('' col-'' + '' -ectomy'') is bowel resection of the large bowel ( colon). It consists of the surgical removal of any extent of the colon, usually segmental resection (partial colectomy). In extreme cases where the entire large intest ...
specimen File:Lung cancer.jpg, A
squamous-cell carcinoma Squamous-cell carcinomas (SCCs), also known as epidermoid carcinomas, comprise a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on th ...
(the whitish tumor) near the
bronchi A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...
in a lung specimen File:BreastCancer.jpg, A large invasive
ductal carcinoma Ductal carcinoma is a type of tumor that primarily presents in the ducts of a gland. Types include: * Mammary **Ductal carcinoma in situ **Invasive ductal carcinoma * Pancreatic ductal carcinoma Pancreatic cancer arises when cells in the p ...
in a
mastectomy Mastectomy is the medical term for the surgical removal of one or both breasts, partially or completely. A mastectomy is usually carried out to treat breast cancer. In some cases, women believed to be at high risk of breast cancer have the operat ...
specimen


Prevention

Cancer prevention is defined as active measures to decrease cancer risk. The vast majority of cancer cases are due to environmental risk factors. Many of these environmental factors are controllable lifestyle choices. Thus, cancer is generally preventable. Between 70% and 90% of common cancers are due to environmental factors and therefore potentially preventable. Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: tobacco, excess weight/
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
, poor diet,
physical inactivity Physical inactivity refers to the lack of moderate-to-vigorous physical activity in a person's lifestyle. It is distinct from sedentary behavior. Health effects The World Health Organization (WHO) has defined physical inactivity as a global public ...
, alcohol, sexually transmitted infections and air pollution. Further, poverty could be considered as an indirect risk factor in human cancers. Not all environmental causes are controllable, such as naturally occurring
background radiation Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of source ...
and cancers caused through hereditary
genetic disorders A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
and thus are not preventable via personal behavior. In
2019 File:2019 collage v1.png, From top left, clockwise: Hong Kong protests turn to widespread riots and civil disobedience; House of Representatives votes to adopt articles of impeachment against Donald Trump; CRISPR gene editing first used to experim ...
, ~44% of all cancer deaths – or ~4.5 M deaths or ~105 million lost
disability-adjusted life year The disability-adjusted life year (DALY) is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. It was developed in the 1990s as a way of comparing the overall health and life ex ...
s – were due to known clearly preventable risk factors, led by smoking, alcohol use and high BMI, according to a GBD systematic analysis.


Dietary

While many dietary recommendations have been proposed to reduce cancer risks, the evidence to support them is not definitive. The primary dietary factors that increase risk are
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...
and alcohol consumption. Diets low in fruits and vegetables and high in red meat have been implicated but reviews and meta-analyses do not come to a consistent conclusion. A 2014 meta-analysis found no relationship between fruits and vegetables and cancer. Coffee is associated with a reduced risk of liver cancer. Studies have linked excessive consumption of
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
or
processed meat Processed meat is considered to be any meat which has been modified in order to either improve its taste or to extend its shelf life. Methods of meat processing include salting, curing, fermentation, smoking, and/or the addition of chemical pr ...
to an increased risk of breast cancer, colon cancer and pancreatic cancer, a phenomenon that could be due to the presence of
carcinogens A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
in meats cooked at high temperatures. In 2015 the
IARC IARC may refer to: * International Aerial Robotics Competition * International Age Rating Coalition * International Agency for Research on Cancer * International Arctic Research Center * Israel Amateur Radio Club The Israel Amateur Radio Club (IA ...
reported that eating
processed meat Processed meat is considered to be any meat which has been modified in order to either improve its taste or to extend its shelf life. Methods of meat processing include salting, curing, fermentation, smoking, and/or the addition of chemical pr ...
(e.g., bacon,
ham Ham is pork from a leg cut that has been preserved by wet or dry curing, with or without smoking."Bacon: Bacon and Ham Curing" in ''Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 2, p. 39. As a processed meat, the term "ham ...
,
hot dogs A hot dog (uncommonly spelled hotdog) is a food consisting of a grilled or steamed sausage served in the slit of a partially sliced bun. The term hot dog can refer to the sausage itself. The sausage used is a wiener ( Vienna sausage) or a f ...
,
sausages A sausage is a type of meat product usually made from ground meat—often pork, beef, or poultry—along with salt, spices and other flavourings. Other ingredients, such as grains or breadcrumbs may be included as fillers or extenders. W ...
) and, to a lesser degree,
red meat In gastronomy, red meat is commonly red when raw and a dark color after it is cooked, in contrast to white meat, which is pale in color before and after cooking. In culinary terms, only flesh from mammals or fowl (not fish) is classified as ...
was linked to some cancers.
Dietary recommendations Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security, or a poor understanding of nutritiona ...
for cancer prevention typically include an emphasis on vegetables, fruit,
whole grains A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm. As part of a general healthy diet, consumption of whole grains is associated wi ...
and fish and an avoidance of processed and red meat (beef, pork, lamb),
animal fats Animal fats and oils are lipids derived from animals: oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial ...
,
pickled foods Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is calle ...
and refined carbohydrates.


Medication

Medications can be used to prevent cancer in a few circumstances. In the general population, NSAIDs reduce the risk of colorectal cancer; however, due to cardiovascular and gastrointestinal side effects, they cause overall harm when used for prevention.
Aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
has been found to reduce the risk of death from cancer by about 7%.
COX-2 inhibitor COX-2 inhibitors are a type of nonsteroidal anti-inflammatory drug (NSAID) that directly targets cyclooxygenase-2, COX-2, an enzyme responsible for inflammation and pain. Targeting selectivity for COX-2 reduces the risk of peptic ulceration and i ...
s may decrease the rate of polyp formation in people with
familial adenomatous polyposis Familial adenomatous polyposis (FAP) is an autosomal dominant inherited condition in which numerous adenomatous polyps form mainly in the epithelium of the large intestine. While these polyps start out benign, malignant transformation into colon ...
; however, it is associated with the same adverse effects as NSAIDs. Daily use of
tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and treat breast cancer in women and men. It is also being studied for other types of cancer. It has b ...
or
raloxifene Raloxifene, sold under the brand name Evista among others, is a medication used to prevent and treat osteoporosis in postmenopausal women and those on glucocorticoids. For osteoporosis it is less preferred than bisphosphonates. It is also used to ...
reduce the risk of breast cancer in high-risk women. The benefit versus harm for 5-alpha-reductase inhibitor such as finasteride is not clear.
Vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
supplementation does not appear to be effective at preventing cancer. While low blood levels of
vitamin D Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group are vitamin D3 (c ...
are correlated with increased cancer risk, whether this relationship is causal and vitamin D supplementation is protective is not determined. One 2014 review found that supplements had no significant effect on cancer risk. Another 2014 review concluded that vitamin D3 may decrease the risk of death from cancer (one fewer death in 150 people treated over 5 years), but concerns with the quality of the data were noted. Beta-Carotene supplementation increases lung cancer rates in those who are high risk.
Folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
supplementation is not effective in preventing colon cancer and may increase colon polyps. Selenium supplementation has not been shown to reduce the risk of cancer.


Vaccination

Vaccine A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified.
s have been developed that prevent infection by some
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
ic viruses.
Human papillomavirus vaccine Human papillomavirus (HPV) vaccines are vaccines that prevent infection by certain types of human papillomavirus (HPV). Available HPV vaccines protect against either two, four, or nine types of HPV. All HPV vaccines protect against at least HP ...
(
Gardasil Gardasil is an HPV vaccine for use in the prevention of certain strains of human papillomavirus (HPV). Text was copied from this source which is copyright European Medicines Agency. Reproduction is authorized provided the source is acknowledge ...
and
Cervarix Cervarix is a vaccine against certain types of cancer-causing human papillomavirus (HPV). Cervarix is designed to prevent infection from HPV types 16 and 18, that cause about 70% of cervical cancer cases. These types also cause most HPV-induced ...
) decrease the risk of developing cervical cancer. The
hepatitis B vaccine Hepatitis B vaccine is a vaccine that prevents hepatitis B. The first dose is recommended within 24 hours of birth with either two or three more doses given after that. This includes those with poor immune function such as from HIV/AIDS and t ...
prevents infection with hepatitis B virus and thus decreases the risk of liver cancer. The administration of human papillomavirus and hepatitis B vaccinations is recommended where resources allow.


Screening

Unlike diagnostic efforts prompted by symptoms and
medical sign Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...
s, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear. This may involve
physical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the pati ...
,
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
or
urine tests A urine test is any medical test performed on a urine specimen. The analysis of urine is a valuable diagnostic tool because its composition reflects the functioning of many body systems, particularly the kidneys and urinary system, and specimens a ...
or medical imaging.
Cancer screening Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, DNA tests, other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection and subsequent treatment ...
is not available for many types of cancers. Even when tests are available, they may not be recommended for everyone. ''
Universal screening Screening, in medicine, is a strategy used to look for as-yet-unrecognised conditions or risk markers. This testing can be applied to individuals or to a whole population. The people tested may not exhibit any signs or symptoms of a disease, or t ...
'' or ''mass screening'' involves screening everyone.Wilson JMG, Jungner G. (1968
Principles and practice of screening for disease.
Geneva:
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
. Public Health Papers, No. 34.
''Selective screening'' identifies people who are at higher risk, such as people with a family history. Several factors are considered to determine whether the benefits of screening outweigh the risks and the costs of screening. These factors include: * Possible harms from the screening test: for example, X-ray images involve exposure to potentially harmful ionizing radiation * The likelihood of the test correctly identifying cancer * The likelihood that cancer is present: Screening is not normally useful for rare cancers. * Possible harms from follow-up procedures * Whether suitable treatment is available * Whether early detection improves treatment outcomes * Whether cancer will ever need treatment * Whether the test is acceptable to the people: If a screening test is too burdensome (for example, extremely painful), then people will refuse to participate. * Cost


Recommendations


U.S. Preventive Services Task Force

The U.S. Preventive Services Task Force (USPSTF) issues recommendations for various cancers: * Strongly recommends cervical cancer screening in women who are sexually active and have a cervix at least until the age of 65. * Recommend that Americans be screened for colorectal cancer via
fecal occult blood Fecal occult blood (FOB) refers to blood in the feces that is not visibly apparent (unlike other types of blood in stool such as melena or hematochezia). A fecal occult blood test (FOBT) checks for hidden (occult) blood in the stool (feces). The ...
testing,
sigmoidoscopy Sigmoidoscopy (from the Greek term for letter " s/ς" + "eidos" + "scopy": namely, to look inside an "s"/"ς"-like object) is the minimally invasive medical examination of the large intestine from the rectum through to the nearest part of the co ...
, or colonoscopy starting at age 50 until age 75. * Evidence is insufficient to recommend for or against screening for
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
,
oral cancer Oral cancer, also known as mouth cancer, is cancer of the lining of the lips, mouth, or upper throat. In the mouth, it most commonly starts as a painless white patch, that thickens, develops red patches, an ulcer, and continues to grow. When on ...
, lung cancer, or prostate cancer in men under 75. * Routine screening is not recommended for
bladder cancer Bladder cancer is any of several types of cancer arising from the tissues of the urinary bladder. Symptoms include blood in the urine, pain with urination, and low back pain. It is caused when epithelial cells that line the bladder become ma ...
,
testicular cancer Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility. Risk factors include an ...
,
ovarian cancer Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...
, pancreatic cancer, or prostate cancer. * Recommends mammography for breast cancer screening every two years from ages 50–74, but does not recommend either
breast self-examination Breast self-examination (BSE) is a screening method used in an attempt to detect early breast cancer. The method involves the woman herself looking at and feeling each breast for possible lumps, distortions or swelling. BSE was once promoted hea ...
or clinical breast examination. A 2013
Cochrane review Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health profes ...
concluded that breast cancer screening by mammography had no effect in reducing mortality because of overdiagnosis and overtreatment.


Japan

Screens for
gastric cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...
using
photofluorography Photofluorography (sometimes called just fluorography) is photography of X-ray images from a fluorescent screen. It is commonly used in some countries for chest X-ray screening, e.g. to diagnose tuberculosis (see Abreugraphy for more information o ...
due to the high incidence there.


Genetic testing

Genetic testing for individuals at high-risk of certain cancers is recommended by unofficial groups. Carriers of these mutations may then undergo enhanced surveillance, chemoprevention, or preventative surgery to reduce their subsequent risk.


Management

Many treatment options for cancer exist. The primary ones include surgery,
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
,
radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...
,
hormonal therapy Hormone therapy or hormonal therapy is the use of hormones in medical treatment. Treatment with hormone antagonists may also be referred to as hormonal therapy or antihormone therapy. The most general classes of hormone therapy are oncologic horm ...
,
targeted therapy Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment ( pharmacotherapy) for cancer, others being hormonal therapy and cytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks ...
and
palliative care Palliative care (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...
. Which treatments are used depends on the type, location and grade of the cancer as well as the patient's health and preferences. The treatment intent may or may not be curative.


Chemotherapy

Chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
is the treatment of cancer with one or more cytotoxic anti-
neoplastic A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
drugs (
chemotherapeutic agents Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothera ...
) as part of a standardized regimen. The term encompasses a variety of drugs, which are divided into broad categories such as
alkylating agents Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...
and
antimetabolite An antimetabolite is a chemical that inhibits the use of a metabolite, which is another chemical that is part of normal metabolism. Such substances are often similar in structure to the metabolite that they interfere with, such as the antifolate ...
s. Traditional chemotherapeutic agents act by killing cells that divide rapidly, a critical property of most cancer cells. It was found that providing combined cytotoxic drugs is better than a single drug, a process called the
combination therapy Combination therapy or polytherapy is therapy that uses more than one medication or modality. Typically, the term refers to using multiple therapies to treat a ''single'' disease, and often all the therapies are pharmaceutical (although it can also ...
, which has an advantage in the statistics of survival and response to the tumor and in the progress of the disease. A Cochrane review concluded that combined therapy was more effective to treat metastasized breast cancer. However, generally it is not certain whether combination chemotherapy leads to better health outcomes, when both survival and toxicity are considered.
Targeted therapy Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment ( pharmacotherapy) for cancer, others being hormonal therapy and cytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks ...
is a form of chemotherapy that targets specific molecular differences between cancer and normal cells. The first targeted therapies blocked the
estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors ( ERα and ERβ), which are members of the ...
molecule, inhibiting the growth of breast cancer. Another common example is the class of Bcr-Abl inhibitors, which are used to treat chronic myelogenous leukemia (CML). Currently, targeted therapies exist for many of the most common cancer types, including
bladder cancer Bladder cancer is any of several types of cancer arising from the tissues of the urinary bladder. Symptoms include blood in the urine, pain with urination, and low back pain. It is caused when epithelial cells that line the bladder become ma ...
, breast cancer, colorectal cancer,
kidney cancer Kidney cancer, also known as renal cancer, is a group of cancers that starts in the kidney. Symptoms may include blood in the urine, lump in the abdomen, or back pain. Fever, weight loss, and tiredness may also occur. Complications can include sp ...
,
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
, liver cancer, lung cancer,
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
, pancreatic cancer, prostate cancer,
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
, and
thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck. C ...
as well as other cancer types. The efficacy of chemotherapy depends on the type of cancer and the stage. In combination with surgery, chemotherapy has proven useful in cancer types including breast cancer, colorectal cancer, pancreatic cancer, osteogenic sarcoma,
testicular cancer Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility. Risk factors include an ...
, ovarian cancer and certain lung cancers. Chemotherapy is curative for some cancers, such as some
leukemias Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or '' ...
, ineffective in some brain tumors, and needless in others, such as most
non-melanoma skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC ...
s. The effectiveness of chemotherapy is often limited by its toxicity to other tissues in the body. Even when chemotherapy does not provide a permanent cure, it may be useful to reduce symptoms such as pain or to reduce the size of an inoperable tumor in the hope that surgery will become possible in the future.


Radiation

Radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...
involves the use of ionizing radiation in an attempt to either cure or improve symptoms. It works by damaging the DNA of cancerous tissue, causing
mitotic catastrophe Mitotic Catastrophe has been defined as either a cellular mechanism to prevent potentially cancerous cells from proliferating or as a mode of cellular death that occurs following improper cell cycle progression or entrance. Mitotic catastrophe can ...
resulting in the death of the cancer cells. To spare normal tissues (such as skin or organs, which radiation must pass through to treat the tumor), shaped radiation beams are aimed from multiple exposure angles to intersect at the tumor, providing a much larger dose there than in the surrounding, healthy tissue. As with chemotherapy, cancers vary in their response to radiation therapy. Radiation therapy is used in about half of cases. The radiation can be either from internal sources (
brachytherapy Brachytherapy is a form of radiation therapy where a sealed radiation source is placed inside or next to the area requiring treatment. ''Brachy'' is Greek for short. Brachytherapy is commonly used as an effective treatment for cervical, prost ...
) or external sources. The radiation is most commonly low energy X-rays for treating skin cancers, while higher energy X-rays are used for cancers within the body. Radiation is typically used in addition to surgery and or chemotherapy. For certain types of cancer, such as early
head and neck cancer Head and neck cancer develops from tissues in the lip and oral cavity (mouth), larynx (throat), salivary glands, nose, sinuses or the skin of the face. The most common types of head and neck cancers occur in the lip, mouth, and larynx. Symptoms ...
, it may be used alone. For painful
bone metastasis Bone metastasis, or osseous metastatic disease, is a category of cancer metastases that results from primary tumor invasion to bone. Bone-originating primary tumors such as osteosarcoma, chondrosarcoma, and Ewing's sarcoma are rare; the most com ...
, it has been found to be effective in about 70% of patients.Holland Chp. 41


Surgery

Surgery is the primary method of treatment for most isolated, solid cancers and may play a role in palliation and prolongation of survival. It is typically an important part of definitive diagnosis and staging of tumors, as biopsies are usually required. In localized cancer, surgery typically attempts to remove the entire mass along with, in certain cases, the lymph nodes in the area. For some types of cancer this is sufficient to eliminate the cancer.Holland Chp. 40


Palliative care

Palliative care Palliative care (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...
is treatment that attempts to help the patient feel better and may be combined with an attempt to treat the cancer. Palliative care includes action to reduce physical, emotional, spiritual and psycho-social distress. Unlike treatment that is aimed at directly killing cancer cells, the primary goal of palliative care is to improve
quality of life Quality of life (QOL) is defined by the World Health Organization as "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards ...
. People at all stages of cancer treatment typically receive some kind of palliative care. In some cases,
medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include those branches of medicine that deal exclusively with children (paediatrics), cancer (oncology), ...
professional organizations A professional association (also called a professional body, professional organization, or professional society) usually seeks to further a particular profession, the interests of individuals and organisations engaged in that profession, and th ...
recommend that patients and physicians respond to cancer only with palliative care. This applies to patients who: # display low
performance status In medicine (oncology and other fields), performance status is an attempt to quantify cancer patients' general well-being and activities of daily life. This measure is used to determine whether they can receive chemotherapy, whether dose adjustment ...
, implying limited ability to care for themselves # received no benefit from prior evidence-based treatments # are not eligible to participate in any appropriate
clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, diet ...
# no strong evidence implies that treatment would be effective Palliative care may be confused with hospice and therefore only indicated when people approach end of life. Like hospice care, palliative care attempts to help the patient cope with their immediate needs and to increase comfort. Unlike hospice care, palliative care does not require people to stop treatment aimed at the cancer. Multiple national medical guidelines recommend early palliative care for patients whose cancer has produced distressing symptoms or who need help coping with their illness. In patients first diagnosed with metastatic disease, palliative care may be immediately indicated. Palliative care is indicated for patients with a prognosis of less than 12 months of life even given aggressive treatment.


Immunotherapy

A variety of therapies using
immunotherapy Immunotherapy or biological therapy is the treatment of disease by activating or suppressing the immune system. Immunotherapies designed to elicit or amplify an immune response are classified as ''activation immunotherapies,'' while immunotherap ...
, stimulating or helping the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...
to fight cancer, have come into use since 1997. Approaches include antibodies, checkpoint therapy, and
adoptive cell transfer Adoptive cell transfer (ACT) is the transfer of cells into a patient. The cells may have originated from the patient or from another individual. The cells are most commonly derived from the immune system with the goal of improving immune functiona ...
.


Laser therapy

Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...
therapy uses high-intensity light to treat cancer by shrinking or destroying tumors or precancerous growths. Lasers are most commonly used to treat superficial cancers that are on the surface of the body or the lining of internal organs. It is used to treat basal cell skin cancer and the very early stages of others like cervical, penile, vaginal, vulvar, and non-small cell lung cancer. It is often combined with other treatments, such as surgery, chemotherapy, or radiation therapy. Laser-induced interstitial thermotherapy (LITT), or interstitial laser photocoagulation, uses lasers to treat some cancers using hyperthermia, which uses heat to shrink tumors by damaging or killing cancer cells. Laser are more precise than surgery and cause less damage, pain, bleeding, swelling, and scarring. A disadvantage is surgeons must have specialized training. It may be more expensive than other treatments.


Alternative medicine

Complementary and alternative cancer treatments are a diverse group of therapies, practices and products that are not part of conventional medicine. "Complementary medicine" refers to methods and substances used along with conventional medicine, while "alternative medicine" refers to compounds used instead of conventional medicine. Most complementary and alternative medicines for cancer have not been studied or tested using conventional techniques such as clinical trials. Some alternative treatments have been investigated and shown to be ineffective but still continue to be marketed and promoted. Cancer researcher Andrew J. Vickers stated, "The label 'unproven' is inappropriate for such therapies; it is time to assert that many alternative cancer therapies have been 'disproven'."


Prognosis

Survival rates vary by cancer type and by the stage at which it is diagnosed, ranging from majority survival to complete mortality five years after diagnosis. Once a cancer has metastasized, prognosis normally becomes much worse. About half of patients receiving treatment for invasive cancer (excluding carcinoma ''in situ'' and non-melanoma skin cancers) die from that cancer or its treatment. A majority of cancer deaths are due to metastases of the primary tumor. Survival is worse in the developing world, partly because the types of cancer that are most common there are harder to treat than those associated with
developed countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
. Those who survive cancer develop a second primary cancer at about twice the rate of those never diagnosed. The increased risk is believed to be due to the random chance of developing any cancer, the likelihood of surviving the first cancer, the same risk factors that produced the first cancer, unwanted side effects of treating the first cancer (particularly radiation therapy), and better compliance with screening. Predicting short- or long-term survival depends on many factors. The most important are the cancer type and the patient's age and overall health. Those who are frail with other health problems have lower survival rates than otherwise healthy people.
Centenarian A centenarian is a person who has reached the age of 100 years. Because life expectancies worldwide are below 100 years, the term is invariably associated with longevity. In 2012, the United Nations estimated that there were 316,600 living centen ...
s are unlikely to survive for five years even if treatment is successful. People who report a higher quality of life tend to survive longer. People with lower quality of life may be affected by depression and other complications and/or disease progression that both impairs quality and quantity of life. Additionally, patients with worse prognoses may be depressed or report poorer quality of life because they perceive that their condition is likely to be fatal. People with cancer have an increased risk of blood clots in their veins which can be life-threatening. The use of
blood thinners Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
such as heparin decrease the risk of blood clots but have not been shown to increase survival in people with cancer. People who take blood thinners also have an increased risk of bleeding. Although extremely rare, some forms of cancer, even from an advanced stage, can heal spontaneously. This phenomenon is known as the
spontaneous remission Spontaneous remission, also called spontaneous healing or spontaneous regression, is an unexpected improvement or cure from a disease that usually progresses. These terms are commonly used for unexpected transient or final improvements in cancer. S ...
.


Epidemiology

Estimates are that in 2018, 18.1 million new cases of cancer and 9.6 million deaths occur globally. About 20% of males and 17% of females will get cancer at some point in time while 13% of males and 9% of females will die from it. In 2008, approximately 12.7 million cancers were diagnosed (excluding
non-melanoma skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC ...
s and other non-invasive cancers) and in 2010 nearly 7.98 million people died. Cancers account for approximately 16% of deaths. The most common are lung cancer (1.76 million deaths), colorectal cancer (860,000) stomach cancer (780,000), liver cancer (780,000), and breast cancer (620,000). This makes invasive cancer the leading cause of death in the
developed world A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
and the second leading in the developing world. Over half of cases occur in the developing world. Deaths from cancer were 5.8 million in 1990. Deaths have been increasing primarily due to longer lifespans and lifestyle changes in the developing world. The most significant
risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often ...
for developing cancer is age. Although it is possible for cancer to strike at any age, most patients with invasive cancer are over 65. According to cancer researcher
Robert A. Weinberg Robert Allan Weinberg (born November 11, 1942) is a biologist, Daniel K. Ludwig Professor for Cancer Research at Massachusetts Institute of Technology (MIT), director of the Ludwig Center of the MIT, and American Cancer Society Research Profes ...
, "If we lived long enough, sooner or later we all would get cancer." Some of the association between aging and cancer is attributed to
immunosenescence Immunosenescence is the gradual deterioration of the immune system, brought on by natural age advancement. A 2020 review concluded that the adaptive immune system is affected more than the innate immune system. Immunosenescence involves both the ...
, errors accumulated in DNA over a lifetime and age-related changes in the
endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
. Aging's effect on cancer is complicated by factors such as DNA damage and inflammation promoting it and factors such as vascular aging and endocrine changes inhibiting it. Some slow-growing cancers are particularly common, but often are not fatal. Autopsy studies in Europe and Asia showed that up to 36% of people have undiagnosed and apparently harmless
thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck. C ...
at the time of their deaths and that 80% of men develop prostate cancer by age 80. As these cancers do not cause the patient's death, identifying them would have represented
overdiagnosis Overdiagnosis is the diagnosis of disease that will never cause symptoms or death during a patient's ordinarily expected lifetime and thus presents no practical threat regardless of being pathologic. Overdiagnosis is a side effect of screening fo ...
rather than useful medical care. The three most common
childhood cancer Childhood cancer is cancer in a child. About 80% of childhood cancer cases can be successfully treated thanks to modern medical treatments and optimal patient care. However, only about 10% of children diagnosed with cancer reside in high-income cou ...
s are
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
(34%),
brain tumor A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and seconda ...
s (23%) and
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
s (12%). In the United States cancer affects about 1 in 285 children. Rates of childhood cancer increased by 0.6% per year between 1975 and 2002 in the United States and by 1.1% per year between 1978 and 1997 in Europe. Death from childhood cancer decreased by half between 1975 and 2010 in the United States.


History

Cancer has existed for all of human history. The earliest written record regarding cancer is from circa 1600 BC in the Egyptian Edwin Smith Papyrus and describes breast cancer.
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...
( – ) described several kinds of cancer, referring to them with the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
word καρκίνος ''karkinos'' (crab or crayfish). This name comes from the appearance of the cut surface of a solid malignant tumor, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name".
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
stated that "cancer of the breast is so called because of the fancied resemblance to a crab given by the lateral prolongations of the tumor and the adjacent distended veins".
Celsus Celsus (; grc-x-hellen, Κέλσος, ''Kélsos''; ) was a 2nd-century Greek philosopher and opponent of early Christianity. His literary work, ''The True Word'' (also ''Account'', ''Doctrine'' or ''Discourse''; Greek: grc-x-hellen, Λόγ ...
( – 50 AD) translated ''karkinos'' into the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''cancer'', also meaning crab and recommended surgery as treatment.
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one ...
(2nd century AD) disagreed with the use of surgery and recommended
purgatives Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...
instead. These recommendations largely stood for 1000 years. In the 15th, 16th and 17th centuries, it became acceptable for doctors to dissect bodies to discover the cause of death. The German professor
Wilhelm Fabry Wilhelm Fabry (also William Fabry, Guilelmus Fabricius Hildanus, or Fabricius von Hilden) (25 June 1560 − 15 February 1634), often called the "Father of German surgery", was the first educated and scientific German surgeon. He is one of the mos ...
believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor Francois de la Boe Sylvius, a follower of Descartes, believed that all disease was the outcome of chemical processes and that acidic
lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues ...
fluid was the cause of cancer. His contemporary
Nicolaes Tulp Nicolaes Tulp (9 October 1593 – 12 September 1674) was a Dutch surgeon and mayor of Amsterdam. Tulp was well known for his upstanding moral character and as the subject of Rembrandt's famous painting ''The Anatomy Lesson of Dr. Nicolaes Tulp' ...
believed that cancer was a poison that slowly spreads and concluded that it was
contagious Contagious may refer to: * Contagious disease Literature * Contagious (magazine), a marketing publication * ''Contagious'' (novel), a science fiction thriller novel by Scott Sigler Music Albums *''Contagious'' (Peggy Scott-Adams album), 1997 * ...
. The physician John Hill described tobacco sniffing as the cause of nose cancer in 1761. This was followed by the report in 1775 by British surgeon
Percivall Pott Percivall Pott (6 January 1714, in London – 22 December 1788) was an English surgeon, one of the founders of orthopaedics, and the first scientist to demonstrate that a cancer may be caused by an environmental carcinogen. Career He was the ...
that
chimney sweeps' carcinoma Chimney sweep's cancer, also called soot wart, is a squamous cell carcinoma of the skin of the scrotum. It has the distinction of being the first reported form of occupational cancer, and was initially identified by Percivall Pott in 1775. It wa ...
, a cancer of the
scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...
, was a common disease among
chimney sweep A chimney sweep is a person who clears soot and creosote from chimneys. The chimney uses the pressure difference caused by a hot column of gas to create a draught and draw air over the hot coals or wood enabling continued combustion. Chimneys ...
s. With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("
metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then ...
"). This view of the disease was first formulated by the English surgeon
Campbell De Morgan Campbell Greig De Morgan (22 November 1811 – 12 April 1876) was a British surgeon who first speculated that cancer arose locally and then spread, first to the lymph nodes and then more widely in the body. His name is used to describe the non c ...
between 1871 and 1874.


Society and culture

Although many diseases (such as heart failure) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboos. The euphemism of "a long illness" to describe cancers leading to death is still commonly used in obituaries, rather than naming the disease explicitly, reflecting an apparent stigma. Cancer is also euphemised as "the C-word"; Macmillan Cancer Support uses the term to try to lessen the fear around the disease. In Nigeria, one local name for cancer translates into English as "the disease that cannot be cured". This deep belief that cancer is necessarily a difficult and usually deadly disease is reflected in the systems chosen by society to compile cancer statistics: the most common form of cancer—non-melanoma
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
s, accounting for about one-third of cancer cases worldwide, but very few deaths—are excluded from cancer statistics specifically because they are easily treated and almost always cured, often in a single, short, outpatient procedure. Western conceptions of
patients' rights A patient's bill of rights is a list of guarantees for those receiving medical care. It may take the form of a law or a non-binding declaration. Typically a patient's bill of rights guarantees patients information, fair treatment, and autonomy o ...
for people with cancer include a duty to fully disclose the medical situation to the person, and the right to engage in
shared decision-making Shared decision-making in medicine (SDM) is a process in which both the patient and physician contribute to the medical decision-making process and agree on treatment decisions. Health care providers explain treatments and alternatives to pa ...
in a way that respects the person's own values. In other cultures, other rights and values are preferred. For example, most African cultures value whole families rather than
individualism Individualism is the moral stance, political philosophy, ideology and social outlook that emphasizes the intrinsic worth of the individual. Individualists promote the exercise of one's goals and desires and to value independence and self-reli ...
. In parts of Africa, a diagnosis is commonly made so late that cure is not possible, and treatment, if available at all, would quickly bankrupt the family. As a result of these factors, African healthcare providers tend to let family members decide whether, when and how to disclose the diagnosis, and they tend to do so slowly and circuitously, as the person shows interest and an ability to cope with the grim news. People from Asian and South American countries also tend to prefer a slower, less candid approach to disclosure than is idealized in the United States and Western Europe, and they believe that sometimes it would be preferable not to be told about a cancer diagnosis. In general, disclosure of the diagnosis is more common than it was in the 20th century, but full disclosure of the prognosis is not offered to many patients around the world. In the United States and some other cultures, cancer is regarded as a disease that must be "fought" to end the "civil insurrection"; a
War on Cancer The "war on cancer" is the effort to find a cure for cancer by increased research to improve the understanding of cancer biology and the development of more effective cancer treatments, such as targeted drug therapies. The aim of such efforts is t ...
was declared in the US. Military metaphors are particularly common in descriptions of cancer's human effects, and they emphasize both the state of the patient's health and the need to take immediate, decisive actions himself rather than to delay, to ignore or to rely entirely on others. The military metaphors also help rationalize radical, destructive treatments. In the 1970s, a relatively popular
alternative cancer treatment Alternative cancer treatment describes any cancer treatment or practice that is not part of the conventional standard of cancer care. These include special diets and exercises, chemicals, herbs, devices, and manual procedures. Most alternative ...
in the US was a specialized form of
talk therapy Talk may refer to: Communication * Communication, the encoding and decoding of exchanged messages between people * Conversation, interactive communication between two or more people * Lecture, an oral presentation intended to inform or instruct ...
, based on the idea that cancer was caused by a bad attitude. People with a "cancer personality"—depressed, repressed, self-loathing and afraid to express their emotions—were believed to have manifested cancer through subconscious desire. Some psychotherapists said that treatment to change the patient's outlook on life would cure the cancer. Among other effects, this belief allowed society to blame the victim for having caused the cancer (by "wanting" it) or having prevented its cure (by not becoming a sufficiently happy, fearless and loving person). It also increased patients' anxiety, as they incorrectly believed that natural emotions of sadness, anger or fear shorten their lives. The idea was ridiculed by Susan Sontag, who published ''
Illness as Metaphor ''Illness as Metaphor'' is a 1978 work of critical theory by Susan Sontag, in which she challenged the victim-blaming in the language that is often used to describe diseases and the people affected by them. Teasing out the similarities between p ...
'' while recovering from treatment for breast cancer in 1978. Although the original idea is now generally regarded as nonsense, the idea partly persists in a reduced form with a widespread, but incorrect, belief that deliberately cultivating a habit of positive thinking will increase survival. This notion is particularly strong in breast cancer culture. One idea about why people with cancer are blamed or stigmatized, called the
just-world hypothesis The just-world hypothesis or just-world fallacy is the cognitive bias that assumes that "people get what they deserve" – that actions will have morally fair and fitting consequences for the actor. For example, the assumptions that noble actions ...
, is that blaming cancer on the patient's actions or attitudes allows the blamers to regain a sense of control. This is based upon the blamers' belief that the world is fundamentally just and so any dangerous illness, like cancer, must be a type of punishment for bad choices, because in a just world, bad things would not happen to good people.


Economic effect

The total health care expenditure on cancer in the US was estimated to be $80.2 billion in 2015. Even though cancer-related health care expenditure have increased in absolute terms during recent decades, the share of health expenditure devoted to cancer treatment has remained close to 5% between the 1960s and 2004. A similar pattern has been observed in Europe where about 6% of all health care expenditure are spent on cancer treatment. In addition to health care expenditure and
financial toxicity Financial toxicity describes the negative impact medical expenses can have on patients in terms of their health related quality of life, leading to negative mental and physical effects as well as, in some cases, bankruptcy, loss of job or income, o ...
, cancer causes indirect costs in the form of productivity losses due to sick days, permanent incapacity and disability as well as premature death during working age. Cancer causes also costs for informal care. Indirect costs and informal care costs are typically estimated to exceed or equal the health care costs of cancer.


Workplace

In the United States, cancer is included as a protected condition by the
Equal Employment Opportunity Commission The U.S. Equal Employment Opportunity Commission (EEOC) is a federal agency that was established via the Civil Rights Act of 1964 to administer and enforce civil rights laws against workplace discrimination. The EEOC investigates discrimination ...
(EEOC), mainly due to the potential for cancer having discriminating effects on workers.U.S. Equal Employment Opportunity Commission. "Questions & Answers about Cancer in the Workplace and the Americans with Disabilities Act (ADA)." https://www.eeoc.gov/laws/types/cancer.cfm Discrimination in the workplace could occur if an employer holds a false belief that a person with cancer is not capable of doing a job properly, and may ask for more
sick leave Sick leave (or paid sick days or sick pay) is paid time off from work that workers can use to stay home to address their health needs without losing pay. It differs from paid vacation time or time off work to deal with personal matters, because sic ...
than other employees. Employers may also make hiring or firing decisions based on misconceptions about cancer disabilities, if present. The EEOC provides interview guidelines for employers, as well as lists of possible solutions for assessing and accommodating employees with cancer.


Research

Because cancer is a class of diseases, it is unlikely that there will ever be a single "
cure for cancer Cancer research is research into cancer to identify causes and develop strategies for prevention, diagnosis, treatment, and cure. Cancer research ranges from epidemiology, molecular bioscience to the performance of clinical trials to evaluate and ...
" any more than there will be a single treatment for all
infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
s.
Angiogenesis inhibitor An angiogenesis inhibitor is a substance that inhibits the growth of new blood vessels ( angiogenesis). Some angiogenesis inhibitors are endogenous and a normal part of the body's control and others are obtained exogenously through pharmaceutical ...
s were once incorrectly thought to have potential as a "
silver bullet In folklore, a bullet cast from silver is often one of the few weapons that are effective against a werewolf or witch. The term ''silver bullet'' is also a metaphor for a simple, seemingly magical, solution to a difficult problem: for example, pe ...
" treatment applicable to many types of cancer. Angiogenesis inhibitors and other cancer therapeutics are used in combination to reduce cancer morbidity and mortality.
Experimental cancer treatment Experimental cancer treatments are mainstream medical therapies intended to treat cancer by improving on, supplementing or replacing conventional methods (surgery, chemotherapy, radiation, and immunotherapy). However, researchers are still tr ...
s are studied in
clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, diet ...
s to compare the proposed treatment to the best existing treatment. Treatments that succeeded in one cancer type can be tested against other types. Diagnostic tests are under development to better target the right therapies to the right patients, based on their individual biology. Cancer research focuses on the following issues: * Agents (e.g. viruses) and events (e.g. mutations) that cause or facilitate genetic changes in cells destined to become cancer. * The precise nature of the genetic damage and the genes that are affected by it. * The consequences of those genetic changes on the biology of the cell, both in generating the defining properties of a cancer cell and in facilitating additional genetic events that lead to further progression of the cancer. The improved understanding of
molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...
and
cellular biology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...
due to cancer research has led to new treatments for cancer since US President
Richard Nixon Richard Milhous Nixon (January 9, 1913April 22, 1994) was the 37th president of the United States, serving from 1969 to 1974. A member of the Republican Party, he previously served as a representative and senator from California and was ...
declared the "
War on Cancer The "war on cancer" is the effort to find a cure for cancer by increased research to improve the understanding of cancer biology and the development of more effective cancer treatments, such as targeted drug therapies. The aim of such efforts is t ...
" in 1971. Since then, the country has spent over $200 billion on cancer research, including resources from public and private sectors. The cancer death rate (adjusting for size and age of the population) declined by five percent between 1950 and 2005. Competition for financial resources appears to have suppressed the creativity, cooperation, risk-taking and original thinking required to make fundamental discoveries, unduly favoring low-risk research into small incremental advancements over riskier, more innovative research. Other consequences of competition appear to be many studies with dramatic claims whose results cannot be replicated and perverse incentives that encourage grantee institutions to grow without making sufficient investments in their own faculty and facilities.
Virotherapy Virotherapy is a treatment using biotechnology to convert viruses into therapeutic agents by reprogramming viruses to treat diseases. There are three main branches of virotherapy: anti-cancer oncolytic viruses, viral vectors for gene therapy and ...
, which uses convert viruses, is being studied. In the wake of the
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickly ...
pandemic, there has been a worry that cancer research and treatment are slowing down.


Pregnancy

Cancer affects approximately 1 in 1,000 pregnant women. The most common cancers found during pregnancy are the same as the most common cancers found in non-pregnant women during childbearing ages: breast cancer, cervical cancer, leukemia, lymphoma, melanoma, ovarian cancer and colorectal cancer. Diagnosing a new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy. As a result, cancer is typically discovered at a somewhat later stage than average. Some imaging procedures, such as
MRIs Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wa ...
(magnetic resonance imaging), CT scans, ultrasounds and
mammograms Mammography (also called mastography) is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through d ...
with fetal shielding are considered safe during pregnancy; some others, such as
PET scans Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...
, are not. Treatment is generally the same as for non-pregnant women. However, radiation and radioactive drugs are normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Early deliveries are often used to advance the start of treatment. Surgery is generally safe, but pelvic surgeries during the first trimester may cause miscarriage. Some treatments, especially certain chemotherapy drugs given during the
first trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...
, increase the risk of
birth defect A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...
s and pregnancy loss (spontaneous abortions and stillbirths). Elective abortions are not required and, for the most common forms and stages of cancer, do not improve the mother's survival. In a few instances, such as advanced uterine cancer, the pregnancy cannot be continued and in others, the patient may end the pregnancy so that she can begin aggressive chemotherapy. Some treatments can interfere with the mother's ability to give birth vaginally or to breastfeed. Cervical cancer may require birth by Caesarean section. Radiation to the breast reduces the ability of that breast to produce milk and increases the risk of
mastitis Mastitis is inflammation of the breast or udder, usually associated with breastfeeding. Symptoms typically include local pain and redness. There is often an associated fever and general soreness. Onset is typically fairly rapid and usually occurs ...
. Also, when chemotherapy is given after birth, many of the drugs appear in breast milk, which could harm the baby.


Other animals

Veterinary oncology, concentrating mainly on cats and dogs, is a growing specialty in wealthy countries and the major forms of human treatment such as surgery and radiotherapy may be offered. The most common types of cancer differ, but the cancer burden seems at least as high in pets as in humans. Animals, typically rodents, are often used in cancer research and studies of natural cancers in larger animals may benefit research into human cancer. Across wild animals, there is still limited data on cancer. Nonetheless, a study published in 2022, explored cancer risk in (non-domesticated) zoo mammals, belonging to 191 species, 110,148 individual, demonstrated that cancer is a ubiquitous disease of mammals and it can emerge anywhere along the mammalian phylogeny. This research also highlighted that cancer risk is not uniformly distributed along mammals. For instance, species in the order Carnivora are particularly prone to be affected by cancer (e.g. over 25% of clouded leopards, bat-eared foxes and
red wolves The red wolf (''Canis rufus'') is a canine native to the southeastern United States. Its size is intermediate between the coyote (''Canis latrans'') and gray wolf (''Canis lupus''). The red wolf's taxonomic classification as being a separate sp ...
die of cancer), while
ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...
s (especially
even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
s) appear to face consistently low cancer risks. In non-humans, a few types of
transmissible cancer A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an oncovirus. Transmission of cancer between humans is rare. The evolution of tra ...
have also been described, wherein the cancer spreads between animals by transmission of the tumor cells themselves. This phenomenon is seen in dogs with
Sticker's sarcoma A canine transmissible venereal tumor (CTVT), also known as a transmissible venereal tumor (TVT), canine transmissible venereal sarcoma (CTVS), sticker tumor and infectious sarcoma, is a histiocytic tumor of the external genitalia of the dog and ...
(also known as canine transmissible venereal tumor), and in
Tasmanian devils The Tasmanian devil (''Sarcophilus harrisii'') (palawa kani: purinina) is a carnivorous marsupial of the family Dasyuridae. Until recently, it was only found on the island states and territories of Australia, state of Tasmania, but it has be ...
with
devil facial tumour disease Devil facial tumour disease (DFTD) is an aggressive non-viral clonally transmissible cancer which affects Tasmanian devils, a marsupial native to Australia. DFTD was first described in 1996. In the subsequent decade the disease ravaged Tasmania's ...
(DFTD).


References


Further reading

* * * * * *


External links

*
"On telling cancer patients to have a positive attitude"
at ''
The Atlantic ''The Atlantic'' is an American magazine and multi-platform publisher. It features articles in the fields of politics, foreign affairs, business and the economy, culture and the arts, technology, and science. It was founded in 1857 in Boston, ...
'' {{Authority control Aging-associated diseases *Cancer Latin words and phrases Wikipedia medicine articles ready to translate