A tumor marker is a substance found in the
blood, urine, or body tissues that can be elevated in cancer, among other tissue types. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncologyto help detect the presence of cancer. An elevated level of a tumor marker can indicate cancer; however, there can also be other causes of the elevation.
Tumor markers can be produced directly by the tumor or by non-tumor cells as a response to the presence of a tumor.
*"Screening" for common
cancers on a population basisExample: elevated prostate specific antigensuggests prostate cancer.
cancersurvivors after treatmentExample: elevated AFP in a child previously treated for teratomasuggests relapsewith endodermal sinus tumor.
*"Diagnosis" of specific tumor types, particularly in certain
brain tumors and other instances where biopsyis not feasible.
tumor antigenis sometimes interchangeably used for tumor marker.
Tumor markers can be classified in two groups: Cancer-specific markers and tissue-specific markers.
Cancer-specific markers are related to the presence of certain cancerous tissue. Because there is a large overlap between the many different tumor tissue types and the markers produced these markers might not be specific in making a diagnosis. They can, however, be useful in the follow-up of treated patients to describe progress of the disease or response to treatment. A few examples of these markers are CEA,
An example of a cancer-specific marker, CEA, or
carcinoembryonic antigen, is a blood-borne protein, first noted to be produced by tumors of the gastrointestinal system. Further investigation showed that it was produced by the occasional lung and breast cancer case, meaning that an elevated level does not necessarily mean a bowel cancer. However, in a patient with a history of a treated bowel cancer, a rising CEA level can be an early sign of recurring bowel cancer. This usually occurs before the site of return can be identified on imaging or examination and so many oncologists question the wisdom of doing a blood test for CEA when the end result is bad news that alarms the patient. Nevertheless, a sequence of steady low CEA readings can provide much needed reassurance to the post-operative patient. Also, a rising sequence of CEA readings should alert the physician to the need for diagnostic tests such as PET scans.
Tissue-specific markers are related to specific tissues which have developed cancer. Generally speaking, these substances are not specifically related to the tumor, and may be present at elevated levels when no cancer is present. But unlike the previous group, elevated levels point to a specific tissue being at fault. Examples include PSA,
beta-HCG- ( Human chorionic gonadotropin), AFP - ( Alpha-fetoprotein), AFP-L3- (a lectin-reactive AFP) and Thyroglobulin. For example, if man has an elevated PSA, a search for prostate cancer will be undertaken. If an individual has an elevated level of beta-HCG, AFP or AFP-L3%, a search for a testicular or liver cancer, respectively, will be made.
Prostate specific antigen) is produced by the normal prostate. It is a protein enzyme called a serine protease that usually acts as an anticoagulant to keep semen liquid. Only small amounts leak into the circulation in normal circumstances. Enlarged prostates leak more substantial amounts, and cancerous prostates also leak substantial amounts. An accurate way to tell if an elevated PSA level results from cancer is to biopsythe prostate.
β-hCG: Elevated levels cannot prove the presence of a tumor, and low levels do not rule it out (an exception is in males who do not naturally produce β-hCG). Nevertheless, elevated βhCG levels fall after successful treatment (e.g. surgical intervention or
chemotherapy), and a recurrence can often be detected by the finding of rising levels.
Application and Interpretation
hook effect(also known as high dose hook effect) is an artifact of tumor marker immunoassay kits, that causes the reported quantity of tumor marker to be incorrectly low when the quantity is high. An undetected hook effect may cause delayed recognition of a tumor.cite journal
author = Leboeuf R, Langlois MF, Martin M, Ahnadi CE, Fink GD
title = "Hook effect" in calcitonin immunoradiometric assay in patients with metastatic medullary thyroid carcinoma: case report and review of the literature
journal = J. Clin. Endocrinol. Metab.
volume = 91
issue = 2
pages = 361–4
year = 2006
pmid = 16278263
doi = 10.1210/jc.2005-1429 ] The hook effect can be detected by analyzing serial dilutions. Absent hook effect, reported quantities of tumor marker in a serial dilution should be proportional to the dilution.
If repeated measurements of tumor marker are needed, some clinical testing laboratories provide a special reporting mechanism, a serial monitor, that links test results and other data pertaining to the person being tested. This requires a unique identifier for the person. In the
United Statescommonly a Social Security numberis used for this. One important function of this mechanism is to ensure that each test is performed using the same assay kit. For example, for AFP many different commercial assay kits, based on different technologies, are available. AFP measurements obtained using different assay kits are not comparable unless special calculations are performed.
proficiency testingfor tumor marker tests, and for clinical tests more generally, is an emerging field.PMID|1540898 [http://www3.interscience.wiley.com/cgi-bin/abstract/112675420/ABSTRACT free full text] ] In the United States, New York state is prominent in advocating such research. [Promoting Safe and Effective Genetic Testing in the United States [http://www.genome.gov/10002403 genome.gov] ]
Wikimedia Foundation. 2010.
Look at other dictionaries:
tumor marker — A substance sometimes found in the blood, other body fluids, or tissues. A high level of tumor marker may mean that a certain type of cancer is in the body. Examples of tumor markers include CA 125 (ovarian cancer), CA 15 3 (breast cancer), CEA… … English dictionary of cancer terms
tumor marker — a circulating biochemical substance indicative of neoplasia; the most useful being specific, sensitive, and proportional to tumor load. Tumor markers may be used to screen, diagnose, assess prognosis, follow response to treatment, and monitor for … Medical dictionary
Tumor marker, CEA — Carcinoembryonic antigen (CEA) is a protein found in many types of cells but associated with tumors and the developing fetus. CEA is tested in blood. The normal range is Benign conditions that can increase CEA include smoking, infection,… … Medical dictionary
Tumor marker, NSE — Neuron specific enolase (NSE) is a substance that has been detected in patients with certain tumors, namely: neuroblastoma, small cell lung cancer, medullary thyroid cancer, carcinoid tumors, endocrine tumors of the pancreas, and melanoma.… … Medical dictionary
serum tumor marker test — A blood test that measures the amount of substances called tumor markers (or biomarkers). Tumor markers are released into the blood by tumor cells or by other cells in response to tumor cells. A high level of a tumor marker may be a sign of… … English dictionary of cancer terms
Tumor M2-PK — is a synonym for the dimeric form of the pyruvate kinase isoenzyme type M2 (PKM2).Tumor M2 PK is a key enzyme within tumor metabolism and can be used in stool (fecal) samples for the screening of colorectal tumors (= bowel cancer) and in EDTA… … Wikipedia
Marker, tumor — Tumor markers are substances that can be detected in higher than normal amounts in the blood, urine, or body tissues of some patients with certain types of cancer. A tumor marker may be made by a tumor itself or by the body in response to the… … Medical dictionary
Tumor antigen — is a substance produced in tumor cells that triggers an immune response in the host. Tumor antigens are useful in identifying tumor cells and are potential candidates for use in cancer therapy. Mechanism of tumor antigenesisNormal proteins in the … Wikipedia
Tumor M2-PK — Pyruvatkinase Isoform M2 Vorhandene Strukturdaten: 1t5a … Deutsch Wikipedia
Tumor-associated calcium signal transducer 1 — Tumor associated calcium signal transducer 1, also known as TACSTD1, is a human gene.cite web | title = Entrez Gene: TACSTD1 tumor associated calcium signal transducer 1| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene Cmd=ShowDetailView… … Wikipedia