CANCER ANTIGEN 125 (SERUM) IS THE STANDARD TUMORMARKER USED TO FOLLOW WOMEN DURING OR AFTER TREATMENT FOR EPITHELIAL OVARIAN CANCER (THE MOST COMMON TYPE OF OVARIAN CANCER.WHEN TO GET TESTED? BEFORE STARTING THERAPY FOR OVARIAN CANCER AND AT INTERVALS DURING AND AFTER TREATMENT; SOMETIMES WHEN YOU HAVE A PELVIC MASS OR ARE AT A HIGH RISK FOR DEVELOPING OVARIAN CANCER. MORE THAN 90% OF WOMEN WITH ADVANCED OVARIAN CANCER HAVE HIGH LEVELS OF CA 125. IF THE CA 125 IS INCREASED AT THE TIME OF DIAGNOSIS, CHANGES IN THE CA 125 CAN BE USED DURING TREATMENT TO GET AN IDEA OF HOW WELL IT’S WORKING.