Survival rate is a part of

survival analysis Survival analysis is a branch of statistics for analyzing the expected duration of time until one event occurs, such as death in biological organisms and failure in mechanical systems. This topic is called reliability theory or reliability analysi ...

. It is the proportion of people in a study or treatment group still alive at a given period of time after diagnosis. It is a method of describing

prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing") is a medical term for predicting the likely or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) or remain sta ...

in certain disease conditions, and can be used for the assessment of standards of therapy. The survival period is usually reckoned from date of diagnosis or start of treatment. Survival rates are based on the population as a whole and cannot be applied directly to an individual. There are various types of survival rates (discussed below). They often serve as endpoints of clinical trials and should not be confused with

mortality rates Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of de ...

, a population metric.

Overall survival

Patient A patient is any recipient of health care services that are performed by healthcare professionals. The patient is most often ill or injured and in need of treatment by a physician, nurse, optometrist, dentist, veterinarian, or other heal ...

s with a certain

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

(for example,

colorectal cancer 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 ...

) can die directly from that disease or from an unrelated cause (for example, a car accident). When the precise

cause of death In law, medicine, and statistics, cause of death is an official determination of conditions resulting in a human's death, which may be recorded on a death certificate. A cause of death is determined by a medical examiner. The cause of death is ...

is not specified, this is called the overall survival rate or observed survival rate. Doctors often use mean overall survival rates to estimate the patient's prognosis. This is often expressed over standard time periods, like one, five, and ten years. For example,

prostate cancer Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that su ...

has a much higher one-year overall survival rate than

pancreatic cancer Pancreatic cancer arises when cells in the pancreas, a glandular organ behind the stomach, begin to multiply out of control and form a mass. These cancerous cells have the ability to invade other parts of the body. A number of types of pancr ...

, and thus has a better prognosis. Sometimes the overall survival is reported as a death rate (%) without specifying the period the % applies to (possibly one year) or the period it is averaged over (possibly five years), e.g
''Obinutuzumab: A Novel Anti-CD20 Monoclonal Antibody for Chronic Lymphocytic Leukemia''

Net survival rate

When someone is interested in how survival is affected by the disease, there is also the net survival rate, which filters out the effect of mortality from other causes than the disease. The two main ways to calculate net survival are

relative survival Relative survival of a disease, in survival analysis, is calculated by dividing the overall survival after diagnosis by the survival as observed in a similar population not diagnosed with that disease. A similar population is composed of individuals ...

and cause-specific survival or disease-specific survival. Relative survival has the advantage that it does not depend on accuracy of the reported cause of death; cause specific survival has the advantage that it does not depend on the ability to find a similar population of people without the disease.

Relative survival

Relative survival Relative survival of a disease, in survival analysis, is calculated by dividing the overall survival after diagnosis by the survival as observed in a similar population not diagnosed with that disease. A similar population is composed of individuals ...

is calculated by dividing the overall survival after diagnosis of a disease by the survival as observed in a similar population that was not diagnosed with that disease. A similar population is composed of individuals with at least age and gender similar to those diagnosed with the disease.

Cause-specific survival and disease-specific survival

Disease-specific survival rate refers to "the percentage of people in a study or treatment group who have not died from a specific disease in a defined period of time. The time period usually begins at the time of diagnosis or at the start of treatment and ends at the time of death. Patients who died from causes other than the disease being studied are not counted in this measurement."

Median survival

Median In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic f ...

survival, or "median overall survival" is also commonly used to express survival rates. This is the amount of time after which 50% of the patients have died and 50% have survived. In ongoing settings such as

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, the median has the advantage that it can be calculated once 50% of subjects have reached the

clinical endpoint Clinical endpoints or clinical outcomes are outcome measures referring to occurrence of disease, symptom, sign or laboratory abnormality constituting a target outcome in clinical research trials. The term may also refer to any disease or sign tha ...

of the trial, whereas calculation of an

arithmetical mean In mathematics and statistics, the arithmetic mean ( ) or arithmetic average, or just the ''mean'' or the ''average'' (when the context is clear), is the sum of a collection of numbers divided by the count of numbers in the collection. The colle ...

can only be done after all subjects have reached the endpoint. The median overall survival is frequently used by the U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

to evaluate the effectiveness of a novel cancer treatment. Studies find that new cancer drugs approved by the U.S.

improve overall survival by a median of 2 to 3 months depending on the sample and analyzed time period: 2.1 months, 2.4 months, 2.8 months.

Five-year survival

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 ...

measures survival at five years after diagnosis.

Disease-free survival, progression-free survival, and metastasis-free survival

cancer research 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 an ...

, various types of survival rate can be relevant, depending on the

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

type and

stage 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 * Sta ...

. These include the disease-free survival (DFS) (the period after curative treatment isease eliminatedwhen no disease can be detected), the

progression-free survival Progression-free survival (PFS) is "the length of time during and after the treatment of a disease, such as cancer, that a patient lives with the disease but it does not get worse". In oncology, PFS usually refers to situations in which a tumor is p ...

(PFS) (the period after treatment when disease hich could not be eliminatedremains stable, that is, does not progress), and the metastasis-free survival (MFS) or distant metastasis–free survival (DMFS) (the period until

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, the ...

is detected). Progression can be categorized as local progression, regional progression, locoregional progression, and metastatic progression.

References

{{reflist Demographics indicators Statistical ratios Epidemiology Survival