tumormarker

A tumor marker is a substance in the body that can indicate the presence of cancer. It is often produced by cancer cells or by normal cells in response to cancer and can be measured in blood, urine, or tissue. Tumor markers are used to help detect cancer, assess prognosis, and monitor treatment or check for recurrence, usually in combination with imaging and biopsy findings.

Common examples include CEA (carcinoembryonic antigen), CA-125, CA 19-9, CA 15-3, CA 27-29, AFP, PSA, and hCG. These markers are associated with specific cancer types but are not perfectly specific or sensitive. For instance, CEA can be elevated in colorectal cancer as well as in smoking or inflammatory conditions; CA-125 may rise with benign gynecologic conditions; AFP can be elevated in liver disease. Some cancers do not produce useful markers at all, and marker levels can vary between individuals.

Tumor markers are most useful for monitoring response to treatment, detecting recurrence, and helping to assess prognosis in certain cancers. They are rarely used alone for screening or diagnosis because elevations can occur for non-cancer reasons and because not all tumors express measurable markers. Serial measurements over time are generally more informative than a single value.

In addition to traditional protein-based markers, newer genomic and molecular indicators such as circulating tumor DNA are increasingly used to monitor tumor burden and guide therapy in some cancers. Laboratory testing is typically performed on blood samples with immunoassays or related methods, with results interpreted in the context of the overall clinical picture.