Serum CA 50 as a tumor marker in pancreatic cancer: a comparison with CA 19-9

CA 50 is a new tumor marker based on a monoclonal antibody (MAb) against a human colorectal carcinoma cell line. The CA 50 antigen is similar, but not identical, to the tumor marker CA 19-9. The serum concentrations of CA 50 were measured by an immunoradiometric assay (CA 50 IRMA) in 95 patients with pancreatic cancer and in 94 patients with benign pancreatic, biliary and hepatocellular diseases. The CA 50 concentration was above the cut-off limit of 17 U/ml in 71% of the patients with pancreatic cancer. Elevated CA 50 levels were also seen in 29% of the patients with benign diseases (up to 250 U/ml), especially in patients with extra-hepatic cholestasis (34%) and hepatocellular jaundice (46%). The results of the immunoradiometric assay were compared to those of the commercially available CA 50 RIA inhibition test. The sensitivities of the two CA 50 assays for pancreatic cancer were similar, but the specificity of the IRMA assay was higher. The CA 50 and CA 19-9 values showed a strong positive correlation and the assay parameters of the tests were almost similar. CA 50 seems a promising tumor marker in the detection and follow-up of patients with pancreatic cancer.