CA 125 (Cancer Antigen 125)

Function

CA 125 is a protein that is a so-called tumor marker. It is found in greater concentration in ovarian cancer cells than in other cells. While it is produced by the surface of the ovary, it can also be produced by other tissues such as the lining of the uterus and the abdominal cavity.

Why it is Ordered

The primary use of CA 125 is to monitor the effectiveness of treatment for ovarian cancer and to check for recurrence. It is also used to evaluate pelvic masses in postmenopausal women to assess the risk of malignancy. It is generally not recommended as a screening tool for the general population because of its low specificity.

Associated Conditions

• Ovarian Cancer: Significantly elevated in roughly 80% of epithelial ovarian cancers.
• Endometrial Cancer: May show elevated levels.
• Endometriosis: A common benign cause of elevation in premenopausal women.
• Pelvic Inflammatory Disease (PID): Infection can cause localized inflammation leading to CA 125 release.
• Cirrhosis: Liver disease can cause elevations due to peritoneal irritation (ascites).

Strategic Monitoring

In oncology, the 'trend' of CA 125 is often more important than a single value. A falling level during chemotherapy usually indicates that the tumor is responding to treatment, while a rising level may suggest the cancer is growing or returning.