CA-125 is a cancer marker most commonly used to detect, monitor the effectiveness of ovarian cancer treatment and detect cancer recurrence after treatment. CA-125 testing done repeatedly over time is often more valuable than testing only once.

CA-125 is an extremely accurate marker for non-mucinous epithelial tumors of the ovary. CA-125 is elevated in more than 80% of women with ovarian cancer. This tumor marker is highly sensitive and specific for ovarian cancer and has been of great help to doctors in making the diagnosis.