A collaborative clinical study of carcinoembryonic antigen in Japan.

A radioimmunoassay for carcinoembryonic antigen with utilization of the so-called sandwich method was established and used for clinical investigation. A collaborative study was made through the cooperation of 34 institutions in Japan, and serum samples from about 400 normal adults, 500 patients with benign diseases, and 1500 cancer patients were assayed. About 90% of the normal adults showed carcinoembryonic antigen levels of under 2.5 ng/ml. The benign disease group showed somewhat higher levels than did the normal group, and the cancer group had levels significantly higher than those of the benign group. The levels were strikingly high in cases of advanced cancer with metastases. The specificity of carcinoembryonic antigen and its antiserum is discussed.