The Carcinoembryonic Antigen (CEA) test is a blood test measuring a protein (CEA) often elevated in certain cancers, especially colorectal, but also breast, lung, & pancreatic, primarily used to monitor cancer treatment effectiveness and recurrence, not to diagnose cancer initially, as high levels can also signal noncancerous conditions like inflammation or smoking. CEA is a tumor marker, normally low in healthy adults, but levels can rise with cancer or other diseases, so it helps track the disease’s progress rather than pinpointing a specific cancer type