Which tumor marker is used to monitor ovarian cancer?

CA 125 is a specific tumor marker that is primarily used to monitor ovarian cancer. It is a glycoprotein that is often elevated in the presence of ovarian tumors, particularly serous papillary cystadenocarcinomas. While CA 125 can also be elevated in several other conditions, such as endometriosis and pelvic inflammatory disease, its significance in monitoring treatment response and disease progression in ovarian cancer patients makes it a valuable tool in clinical practice.

The role of CA 125 extends beyond just diagnosis; it is commonly used to gauge the effectiveness of therapy, detect recurrences, and sometimes even assess prognosis. Elevated levels of CA 125 after treatment can indicate a recurrence of the disease, while decreasing levels may suggest that treatment is working.

In contrast, other markers listed, such as PSA (prostate-specific antigen), CEA (carcinoembryonic antigen), and AFP (alpha-fetoprotein), are utilized for other types of cancers. PSA is primarily associated with prostate cancer, CEA is used mainly for colorectal cancer, and AFP is associated with liver cancer and germ cell tumors. Thus, CA 125's targeted application for ovarian cancer monitoring distinguishes it as the appropriate answer in this case.