What is CA-125?

CA-125, which stands for “Cancer Antigen 125” is a protein that may be found in high amounts in the blood of patients with ovarian cancer.  CA-125 is produced on the surface of cells and is released in the blood stream.  This protein is elevated in more than 80 percent of women with advanced ovarian cancers, and in 50 percent of those with early-stage cancers.

The CA-125 test is among the blood tests that may be ordered by a doctor if ovarian cancer is suspected.

Because CA-125 misses half of early cancers and can be elevated by benign conditions, such as diverticulitis, endometriosis, liver cirrhosis, pregnancy, and uterine fibroids, the National Cancer Institute and the United States Preventive Services Task Force do not endorse using it to screen women for ovarian cancer who are at ordinary risk or in the general population.  Research on new ways to use CA-125 to more accurately identify ovarian cancer is underway.

CA-125, however, is approved by the Food and Drug Administration to monitor the effectiveness of treatment for ovarian cancer and for detecting disease recurrence after treatment.