Tumor Marker Tests

Tumor markers are specific substances found in the blood, urine or body tissues that arise from cells and are often elevated in cancer. These markers are either produced by the tumor, are elevated because of the tumor’s effect on cells around it or are produced in response to the tumor.

The first marker groups are related to the presence of cancerous tissue, and unfortunately these markers tend to be very unhelpful in making a diagnosis (because there is a large overlap between the many different tumor types and the markers produced). They can, however, be useful in follow up of treated patients to describe progress of the disease before any further masses can be found clinically or by imaging. A few examples of these markers are CEA, CA19-9, and CA125.

CEA, or carcinoembryonic antigen, is a blood-borne protein, first noted to be produced by tumors of the gastrointestinal system.

PSA or Prostate specific antigen is produced by the normal prostate gland. 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 thereby raising the PSA level.