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.