CA125 is a glycoprotein that is present on the surface of most ovarian cancer cells and is used primarily to monitor treatment of ovarian cancer and to determine whether it has recurred. 95% of healthy adult women have CA125 levels ≤35 units/mL. If a patient’s serum CA125 level is twice the baseline level, physical examination, vaginal ultrasound, and CT should be performed immediately.
Elevated CA125 can be seen in ovarian, breast, pancreatic, and gastric cancers, as well as cancers of the liver, lung, colon, gallbladder, uterus, fallopian tubes, breast, and endometrium; consider ovarian cancer if CA125 is elevated 2 to 5 times. In addition to malignant tumors, benign diseases such as ovarian cysts, pelvic inflammatory disease, endometriosis, cirrhosis, hepatitis, and physiological changes such as early pregnancy and menstrual cycle, CA125 can also be elevated to varying degrees.
CA125 levels are differentially elevated in benign and malignant exudate, serum, and plasma, and thus are not highly specific, which, combined with the lack of sensitivity of CA125 for early disease, makes it inappropriate for screening of the ovarian cancer population, but rather suitable for follow-up surveillance.