What are tumor markers?
Tumor markers are substances, often proteins, that are produced by the cancer tissue itself or sometimes by the body in response to cancer growth.
While tumor marker tests can provide very useful information, they do have limitations:
- Many tumor markers may also be elevated in persons with diseases other than cancer.
- Some tumor markers are specific for a particular type of cancer, while others are seen in several different types of cancer.
- Not every person with a particular type of cancer will have an elevated level of the corresponding tumor marker.
- Not every cancer has a tumor marker that has been identified as associated with it.
Consequently, tumor markers alone are not diagnostic for cancer; for some types of cancer, they provide additional information that can be considered in conjunction with a patient’s medical history and physical exam as well as other laboratory and/or imaging tests.
How are tumor markers used?
Because most tumor markers are not sensitive or specific enough, these tests are not well suited for screening the general population; however, a few may be used to screen people who are at high risk because they have a strong family history or specific risk factors for a particular cancer.
In a person who has symptoms, tumor markers may be used to help detect the presence of cancer and help differentiate it from other conditions with similar symptoms.
If a person does have cancer, tumor marker elevations can be used to help determine whether the cancer has spread (metastasized) to other tissues and organs and to what extent.
Some tumor markers can be used to help determine how aggressive a cancer is likely to be.
Guide choice of treatment
A few tumor markers provide information about which treatments might be effective against a person’s cancer. This is a growing area of research. For more information, see the article Genetic Tests for Targeted Cancer Therapy.
Monitor success of treatment and detect recurrence
Tumor markers can be used to monitor the effectiveness of treatment, especially in advanced cancers. If the marker level drops, the treatment is working; if it stays elevated, adjustments are needed. (The information must be used with care, however, since other conditions can sometimes cause tumor markers to rise or fall.) One of the most important uses for tumor markers, along with guiding treatment, is to monitor for cancer recurrence. If a tumor marker is elevated before treatment, low after treatment, and then begins to rise over time, then it is likely that the cancer is returning. (If it remains elevated after surgery, then chances are that not all of the cancer was removed.)