Current status of carcinoembryonic antigen assay.

The carcinoembryonic antigen (CEA) is a glycoprotein that can be measured by radioimmunoassay and other immunologic techniques. The CEA reagent is currently commercially available in kit form and has been found to be satisfactory for laboratory use. The highest percentage of elevated plasma CEA and the highest CEA titer have been found in patients with entodermally derived tumors. CEA has also been detected in patients with other tumors and in patients with nonneoplastic disease, as well as in heavy cigarette smokers. The present CEA assay cannot be used to screen for cancer in the general population. The greatest clinical usefulness of current CEA assay is in assessing prognosis, in the detection of residual tumors and recurrent disease, and in monitoring chemotherapy and radiotherapy. The use of anti-CEA antiserum as a tumor-localizing agent may be of potential value in the future.