CA 125

CA 125 is produced by a variety of cells, but particularly by ovarian cancer cells. Studies have shown that many women with ovarian cancer have elevated CA 125 levels. CA 125 is used primarily in the management of treatment for ovarian cancer. In women with ovarian cancer being treated with chemotherapy, a falling CA 125 level generally indicates that the cancer is responding to treatment. Increasing CA 125 levels during or after treatment, on the other hand, may suggest that the cancer is not responding to therapy or that some cancer cells remain in the body. Doctors may also use CA 125 levels to monitor patients for recurrence of ovarian cancer.
Not all women with elevated CA 125 levels have ovarian cancer. CA 125 levels may also be elevated by cancers of the uterus, cervix, pancreas, liver, colon, breast, lung, and digestive tract. Noncancerous conditions that can cause elevated CA 125 levels include endometriosis, pelvic inflammatory disease, peritonitis, pancreatitis, liver disease, and any condition that inflames the pleura (the tissue that surrounds the lungs and lines the chest cavity). Menstruation and pregnancy can also cause an increase in CA 125.

http://www.doctorslounge.com/oncology/labs/ca125.htm
http://www.nlm.nih.gov/medlineplus/ency/imagepages/9627.htm