The cancer antigen 125 test is used to diagnose the recurrence of ovarian cancer, according to the University of Texas MD Anderson Cancer Center. Physicians often check the CA 125 levels in patients who previously suffered from ovarian cancer to see how these levels have changed over time.
CA 125 is a protein that is found on the surface of most ovarian cancer cells, reports WebMD. The protein is released by the cancer cells into the bloodstream, explains Fujirebio Diagnostics. A simple blood test can be used to determine the levels of CA 125 in the blood.
However, this method of diagnosing a patient who has a low risk of cancer or who has never suffered from ovarian cancer before yields a lot of false positives, explains the University of Texas MD Anderson Cancer Center. This is because elevated levels of this protein do not always mean that the patient suffers from ovarian cancer, according to Mayo Clinic.
However, CA 125 has proven to be very effective in the management of ovarian cancer, states Fujirebio Diagnostics. Reduced levels of CA 125 usually mean that the ovarian cancer treatment is working, reports the American Cancer Society. The CA 125 is also useful in determining whether the ovaries were the original site of the cancer, notes WebMD. If the cancer has spread to another organ, high levels of CA 125 may indicate that the source of the cancer is the ovaries.