A tumor marker is a

biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, ...

that can be used to indicate the presence of

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

or the behavior of cancers (measure progression or response to therapy). They can be found in

bodily fluids Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the body of an organism. In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women ...

or tissue. Markers can help with assessing prognosis, surveilling patients after surgical removal of tumors, and even predicting drug-response and monitor therapy. Tumor markers can be molecules that are produced in higher amounts by cancer cells than normal cells, but can also be produced by other cells from a reaction with the cancer. The markers can't be used to give patients a diagnosis but can be compared with the result of other tests like biopsy or imaging.

Classification

Tumor markers can be

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

s, receptors and gene products. Proteins include

hormone A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physio ...

s and

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s. To detect enzyme tumor markers enzyme activity is measured. They were previously widely used, but they have largely been replaced by

oncofetal antigen Oncofetal antigens are proteins which are typically present only during fetal development but are found in adults with certain kinds of cancer. These proteins are often measurable in the blood of individuals with cancer and may be used to both diag ...

s and

monoclonal antibodies A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a Lineage (evolution), cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Mon ...

, due to disadvantages such as most of them lacking organ specificity. Carbohydrates consists of antigens on and/or secreted from tumor cells, these are either high-molecular weight mucins or blood group antigens. Receptors are used to determine prognosis and measure how the patient responds to treatment, while genes or gene product can be analyzed to identify mutations in the genome or altered gene expression.

Uses

Tumor markers may be used for the following purposes: * Monitoring the malignancy When a

malignant tumor 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 ...

is found by the presence of a tumor marker, the level of marker found in the body can be monitored to determine the state of the tumor and how it responds to treatment. If the quantity stays the same during treatment it can indicate that the treatment isn't working, and an alternative treatment should be considered. Rising levels of tumor marker does not necessarily reflect a growing malignancy but can result from things like unrelated illnesses. * Reflect the stage of cancer By determining the stage of cancer, it's possible to give a prognosis and treatment plan. * Screening for cancers No screening test is wholly specific, and a high level of tumor marker can still be found in benign tumors. The only tumor marker currently used in screening is PSA (prostate-specific antigen). * Diagnostics Tumor markers alone can't be used for diagnostic purposes, due to lack of sensitivity and specificity. The only approved diagnostic method for cancer is with a

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

. * Detects reoccurring cancers Tumor markers can detect reoccurring cancers in patients post-treatment.

Techniques

Tumor markers can be determined in serum or rarely in urine or other body fluids, often by

immunoassay An immunoassay (IA) is a biochemical test that measures the presence or concentration of a macromolecule or a small molecule in a solution through the use of an antibody (usually) or an antigen (sometimes). The molecule detected by the immunoassay ...

, ⁣⁣ but other techniques such as

activity determination are sometimes used. Assaying tumor markers were significantly improved after the creation of

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of ...

and

RIA A ria (; , feminine noun derived from ''río'', river) is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. Definitions Typically rias have a dendriti ...

techniques and the advancement of

in the 1960s and 1970s. For many assays, different assay techniques are available. It is important that the same assay is used, as the results from different assays are generally not comparable. For example, mutations of the p53 gene can be detected through immunohistochemical polymorphism screening of DNA, sequence analysis of DNA, or by single-strand conformational polymorphism screening of DNA. Each assay may give different results of the clinical value of the p53 mutations as a prognostic factor. Interlaboratory proficiency testing for tumor marker tests, and for clinical tests more generally, is routine in Europe and an emerging field in the United States.

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

state is prominent in advocating such research.

List of commonly used markers

Accuracy and specific use

The ideal tumor marker has the following characteristics: * Specificity to a certain type of tumor * Should detect the malignancy earlier than a clinical diagnosis * Be highly sensitive to avoid false positives * The level of tumor marker should indicate the state of the malignancy to be able to monitor treatment response. An ideal tumor marker does not exist, and how they are clinically applied depends on the specific tumor marker. For example, tumor markers like Ki-67 can be used to choose form of treatment or in prognostics but are not useful to give a diagnosis, while other tumor markers have the opposite functionality. Therefore it's important to follow the guidelines of the specific tumor marker. Tumor markers are mainly used in clinical medicine to support a diagnosis and monitor the state of malignancy or reocurrence of cancer.

References

External links

* * {{Authority control Biomarkers