What is the CA 125 cancer detection test?
CA-125 is a blood test used to evaluate ovarian cancer treatment. CA-125 is a protein that is found more in ovarian cancer cells than in other cells. This protein enters the bloodstream and can be measured by a blood test. There are two CA-125 tests: a first and second generation test. The second generation test is now more widely used and is generally more accurate.
The test is often used to follow women who have already been diagnosed with ovarian cancer. In these cases, the CA-125 is a very good indicator of whether a patient is responding to treatment, and whether a patient remains in remission after treatment. In general, the CA-125 is not a good test to screen healthy women for ovarian cancer.
Normal Results
The normal values for a CA-125 depend on the lab running the test. In general, levels above 35 U/mL are considered abnormal.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What do Abnormal Results Mean?
In a woman with known ovarian cancer, a rise in CA-125 usually means that the disease has progressed or recurred. A decrease in CA-125 usually means the disease is responding to treatment.
In a woman who has NOT already been diagnosed with ovarian cancer, an elevated CA-125 can mean a number of things. While it can indicate that she has ovarian cancer, it can also indicate other types of cancer, as well as several benign diseases such as endometriosis. When used in healthy women, an elevated CA-125 usually does NOT mean ovarian cancer is present. The vast majority of healthy women with an elevated CA-125 do not have ovarian cancer (or any other cancer for that matter). The "false positive" rate for this group of women is high.
Any woman with an abnormal CA-125 test will need further tests, and sometimes invasive surgical procedures, to confirm the result. These additional tests all involve risks and anxiety. Therefore, the CA-125 should not be considered an effective general screening test for ovarian cancer. Studies are underway to determine whether it might be effective when combined with other blood tests or radiologic studies.
Review Date: 6/10/2008 Reviewed By: James R. Mason, MD, Oncologist, Director, Blood and Marrow Transplantation Program and Stem Cell Processing Lab, Scripps Clinic, Torrey Pines, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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