Carcinoembryonic Antigen (CEA) in Colonic Cancer

Radioimmunoassay for serum carcinoembryonic antigen (CEA) was performed in 127 colonic cancer patients. The test results were positive in 57 (72%) of 79 patients in whom tumor was present at the time of assay. In the 51 patients tested prior to tumor resection, the incidence of positivity varied from 19% in those with localized tumors to 100% in those with metastatic disease. Preoperatively, undetectable CEA in patients with known colonic cancer suggested localized tumor and good prognosis. Strongly positive CEA test results in such patients correlated with extensive tumors and poor prognosis. Postoperatively, a positive result for serum CEA indicated presence of residual tumor. A negative CEA test result postoperatively, however, did not exclude residual tumor. Periodic CEA determination in the patients who have undergone resection of colonic cancer may detect tumor recurrence that is at a treatable stage.