CA-125 is marker for: September 2007
**Core Concept**
CA-125 is a tumor marker for ovarian cancer, specifically used to monitor disease recurrence and response to treatment in patients with epithelial ovarian cancer. It is a mucin-type glycoprotein that is overexpressed on the surface of ovarian cancer cells.
**Why the Correct Answer is Right**
CA-125 is elevated in approximately 80% of patients with epithelial ovarian cancer, particularly in those with stage III and IV disease. The antigen is shed into the peritoneal fluid and bloodstream, where it can be detected using immunoassays. Elevated CA-125 levels are associated with tumor recurrence and progression, but they can also be elevated in benign conditions such as endometriosis, pelvic inflammatory disease, and during the menstrual cycle.
**Why Each Wrong Option is Incorrect**
**Option A:** CA-125 is not a marker for breast cancer, which is typically associated with other tumor markers such as CA 15-3 and CA 27.29.
**Option B:** CA-125 is not a marker for lung cancer, which is typically associated with other tumor markers such as CYFRA 21-1 and NSE.
**Option C:** CA-125 is not a marker for colon cancer, which is typically associated with other tumor markers such as CEA and CA 19-9.
**Clinical Pearl / High-Yield Fact**
It is essential to note that CA-125 is not a reliable screening test for ovarian cancer, as it can be elevated in benign conditions and is not specific to ovarian cancer. However, it can be useful in monitoring disease recurrence and response to treatment in patients with epithelial ovarian cancer.
**Correct Answer:** A.