Carcinoembryonic antigen is a glycoprotein and is used for monitoring treatment of which cancer?

• A. Lung cancer
• B. Colon cancer
• C. Breast cancer
• D. Prostate cancer

Answer: (B)

Carcinoembryonic antigen is a tumor marker whose levels reflect tumor burden in colorectal cancer, making it useful for monitoring how well treatment is working and for detecting recurrence after therapy. It’s a glycoprotein produced during fetal development and kept at low levels in healthy adults, but many colorectal cancers secrete CEA, so serial measurements help track response to treatment. However, CEA isn’t perfectly specific—it can be elevated in smokers, inflammatory conditions, and other cancers—so it’s not used alone for screening or diagnosis. In other cancers like lung, breast, or prostate, CEA may rise but it isn’t the primary marker for monitoring compared with colorectal cancer. So the cancer most appropriately monitored with CEA is colon (colorectal) cancer.