What are they? Tumor markers are substances, usually
proteins, that are produced by the body in response to cancer growth or by the cancer tissue itself. Some tumor markers are specific, while others are seen in several cancer types. Many of the well-known markers are also seen in non-cancerous conditions. Consequently, these tumor markers are not diagnostic for cancer.
There are only a handful of well-established tumor markers that are being routinely used by physicians. Many other potential markers are still being researched. Some marker tests cause great excitement when they are first discovered but, upon further investigation, prove to be no more useful than markers already in use.
The goal is to be able to screen for and diagnose cancer early, when it is the most treatable and before it has had a chance to grow and spread. So far, the only tumor marker to gain wide acceptance as a general screen is the
Prostate Specific Antigen (PSA) for men. Other markers are either not specific enough (too many
false positives, leading to expensive and unnecessary follow-up testing) or they are not elevated early enough in the disease process.
Some people are at a higher risk for particular cancers because they have inherited a genetic mutation. While not considered tumor makers, there are tests that look for these mutations in order to estimate the risk of developing a particular type of cancer.
BRCA1 and BRCA2 are examples of gene
mutations related to an inherited risk of
breast cancer and
ovarian cancer. For more information, see our
overview on genetic testing.
