Initial clinical evaluation of an immunoradiometric assay for CA 19-9 using the NCI serum bank.

More than 1,600 coded sera obtained from blood donors and the NCI/Mayo Clinic Serum Bank were analyzed with an improved immunoradiometric assay for the carbohydrate antigenic determinant, CA 19-9. Results indicated that CA 19-9 is elevated in a large fraction of sera (67%) from patients with advanced adenocarcinomas of the upper gastrointestinal (GI) tract, including those with pancreatic, hepatobiliary and gastric carcinomas. Several of these sera had CA 19-9 exceeding 300,000 U/ml. A smaller fraction (18%) of patients with carcinomas of the large bowel had elevated serum CA 19-9 levels, the majority among patients with metastatic disease. In contrast, none of the healthy donors from the serum bank and only 4 of 1,023 of the blood donor specimens (0.4%) had CA 19-9 levels greater than or equal to 40 U/ml. Three of 235 sera (1.3%) from benign disease patients had levels of CA 19-9 in excess of 40 U/ml. These data suggest that the improved CA 19-9 immunoradiometric assay may have clinical utility as a diagnostic adjunct for adenocarcinoma of the upper GI tract and that the assay also may have some value in monitoring patients with advancing colorectal carcinoma, particularly in combination with CEA determinations. Rigorous prospective clinical trials will be necessary to verify these hypotheses.