Cancer Antigen 125 (CA-125)

CA-125 (Cancer Antigen) Test, Carbohydrate Antigen (CA-125) Test

Why It Is Done

The test for cancer antigen 125 (CA-125) is used to:

• Check if treatment for cancer is working. If the level of CA-125 is going down, it usually means that the treatment is working.
• Check if cancer has returned.
• Check if the ovary is the main site of cancer in a woman. If a cancer is found at another site (metastatic cancer), a higher-than-normal CA-125 test result may mean that ovarian cancer is the main site. However, other types of cancer also can increase CA-125 levels.

The CA-125 test is not recommended as a screening test for ovarian cancer at this time. However, the CA-125 test and an ultrasound scan may be used to test women who have a high chance for ovarian cancer. Women have a high risk of ovarian cancer if they have a family history of ovarian cancer or certain changes (mutations) in their DNA (such as the breast cancer BRCA1 mutation).

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Author:	Maria G. Essig, MS, ELS	Last Updated: August 15, 2007
Medical Review:	Adam Husney, MD - Family Medicine Anne C. Poinier, MD - Internal Medicine Douglas A. Stewart, MD - Medical Oncology
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