What is a tumor marker and what do the numbers mean?

Tumor Markers
Tumor markers are substances, usually proteins, that are produced by the body in response to cancer growth or by the cancer tissue itself and that may be detected in blood, urine, or tissue samples. Some tumor markers are specific for a particular type of cancer, while others are seen in several cancer types. Most of the well-known markers may also be elevated in non-cancerous conditions. Consequently, tumor markers alone are not diagnostic for cancer.

A tumor marker can be higher when there is cancer present. There are many different tumor markers. Each different one tells the doctor about a particular disease process. They are used in oncology to detect the presence of cancer. An elevated level of a tumor marker can indicate cancer; but, there can also be other causes of the elevated tests.

Tumor markers can be produced directly by the tumor or by non-tumor cells as a response to the presence of a tumor. Most tumor markers are tumor antibodies, but not all tumor antibodies can be used as tumor markers. So they are just one test among all the tests that a doctor will be using to monitor the disease.

Most tests are a blood test and laboratories do specific chemical analysis of the blood or also urine. The names of some tests are AFP, (Alpha-Fetoprotein); CEA, (Carcinoembryonic antigen); CA125 is elevated in many cancers including endometrial, pancreatic, lung, breast, and colon cancer; CA19-9 is a antibody against a colon cancer; the PSA screening test is a blood test that looks for a specific tumor marker in prostate cancer.