CA-125 is primarily used to monitor therapy during treatment for ovarian cancer. CA-125 is also used to detect whether cancer has come back after treatment is complete. A series of CA-125 tests that shows rising or falling concentrations is often more useful than a single result.
CA-125 is sometimes used to test and monitor high-risk women who have a family history of ovarian cancer but who do not yet have the disease. The test is not used, however, to screen women for ovarian cancer because it is non-specific. In 2012, the U.S. Preventive Services Task Force reaffirmed a 2008 recommendation against screening women for ovarian cancer. This recommendation applies to asymptomatic women but not to women at high risk for developing ovarian cancer, such as those with a genetic mutation.
Sometimes a CA-125 test may be ordered along with a transvaginal ultrasound to help detect early ovarian cancer in those at high risk of developing the disease. It may also sometimes be ordered to help investigate a pelvic mass.
The CA-125 test is not recommended for routine use. A doctor may order a CA-125 test before a woman starts ovarian cancer treatment as a baseline to compare against future measurements. During therapy, physicians order CA-125 testing at intervals to monitor response to therapy. CA-125 may also be measured periodically after therapy is completed. An increase in CA-125 may indicate that the cancer has returned.
In some cases, a doctor may order a CA-125 when a woman has a pelvic mass in order to help determine the cause. Some doctors may order a CA-125 and a transvaginal ultrasound when a woman is at high risk of developing ovarian cancer.
If CA-125 levels fall during therapy, this generally indicates that the cancer is responding to treatment. If CA-125 levels rise or stay the same, then the cancer may not be responding to therapy. High CA-125 levels after treatment is complete may indicate that the cancer has come back.
If a woman who has been diagnosed with ovarian cancer has a baseline CA-125 level that is normal, then the test is not likely to be useful to monitor her ovarian cancer. In this case, the ovarian cancer may not be producing CA-125 and is not a good marker of disease progression.
In a woman with a pelvic mass, and in a woman with a high risk for developing ovarian cancer, a significantly elevated CA-125 is a concern but does not necessarily indicate ovarian cancer. This finding would prompt further testing and evaluation.
A new tumor marker, HE4 (Human Epididymis Protein), may be ordered along with CA-125 to monitor epithelial cell tumors, the most common type of ovarian cancers. These cancers develop from the cells that cover the outside of the ovaries. The use and full clinical utility of this test has yet to be determined.
This article was last reviewed on November 15, 2012. | This article was last modified on December 29, 2014.
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