Which marker is used to monitor colorectal and other GI cancers, and is elevated in colorectal cancer?

• A. CA-125
• B. CEA
• C. AFP
• D. HCG

Answer: (B)

Carcinoembryonic antigen (CEA) is used to monitor colorectal and other GI cancers because its level in the blood generally rises with tumor burden and falls when the cancer responds to treatment. Serial measurements of CEA help clinicians track how well therapy is working and detect possible recurrence after surgery. It’s helpful for monitoring, but not ideal for screening, since its sensitivity and specificity aren’t sufficient for detecting early disease and it can be elevated in non-malignant conditions and in smokers.

Other markers listed have different primary associations: CA-125 is mainly used in ovarian cancer, AFP is elevated in hepatocellular carcinoma and certain germ cell tumors, and HCG is associated with pregnancy and some germ cell tumors.