What is the CA-125 Blood Test?
Typically, the CA-125 test is used to monitor women who have been diagnosed with ovarian cancer. If the CA-125 levels were high when the cancer was first diagnosed, the test is used as a tool to determine if ovarian cancer treatment is working. Usually a patient will have the test completed every 2-4 months after surgery and chemotherapy and then less frequently as time progresses.
Another reason a CA-125 test may be done is to help diagnose when symptoms or findings suggest ovarian cancer. It is not usually done as a screening test for healthy women, but rather as a supporting test to assist with diagnosis.
CA-125 is a test done on a blood sample drawn in a laboratory. The assay (analysis) assesses the amount of an antibody that recognizes an antigen in tumor cells.
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).
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.
Is the CA-125 Helpful for Diagnosis?
Slightly over 80 percent of women who have ovarian cancer will have an elevated CA-125 in the liquid portion of their blood (serum) at the time of diagnosis. (True positive).
CA-125 tests can generate a false positive so this is why it is ordered along with a transvaginal sonography and a pelvic exam. False positives are more likely to occur with pre-menopausal women than post-menopausal women. It is important to note that almost 20% of women who have ovarian cancer do not ever have elevated CA-125 and therefore it is essential to use the test in addition to a physical exam.
If a woman has 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.
What if I have an elevated CA-125
If a woman hasn’t been diagnosed with ovarian cancer, an elevated CA-125 could indicate:
- Ovarian Cancer
- Another Type of Cancer
- False Positive
Therefore, the CA-125 should not be considered an effective general screening test for ovarian cancer.