Tests for carcinoembryonic antigen. Role in diagnosis and management of cancer

THE CARCINOEMBRYONIC antigen (CEA) of the human digestive system was first described in 1965 after a series of experiments involving the immunization of heterologous animals with human-colon cancer-tissue extracts and the preparation of antitumor antisera under well-defined conditions. The CEA has been purified, identified as a fairly large glycoprotein, and partly characterized with regard to its protein and carbohydrate constituents. Several review articles¹⁻⁴detail these developments. At least a portion of the CEA of colon cancer cells has been localized, by immunoelectron microscopy, to the cellular glycocalyx.¹From this position, where it may represent a structural constituent of the glycocalyx or material in transit from the cytoplasm across the cell membrane, the CEA is apparently quite easily released into the surrounding body fluids. Radioimmunoassay Techniques Since 1969, a number of sensitive and reproducible radioimmunoassays for CEA have been developed that are capable of detecting nanogram quantities of this