How are tumor markers used?
Tumor markers may be used for a variety of purposes. However, they are not typically used alone. Depending on the type of cancer, they may be used in conjunction with a tissue biopsy or a bone marrow or blood smear examination, for example, and/or with other tumor markers. They are not definitive but provide additional information that can be used to help:
- Screen. 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.
- Diagnose. 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.
- Stage. 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.
- Determine prognosis. 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.)
Examples of tumor markers that are used in each of these ways are provided in the table on the next page of this article.