Measurement of a monoclonal-antibody-defined antigen (CA19-9) in the sera of patients with malignant and nonmalignant diseases. Comparison with carcinoembryonic antigen.

Immunoradiometric assay (IRMA) using monoclonal antibody for colon cancer cell surface antigen (CA19-9) was compared with carcinoembryonic antigen (CEA) with regard to sensitivity and specificity in 730 patients. In the 341 patients who had no evidence of malignant disease, CA19-9 levels ranged between less than 1.5 to 49 U/ml. Specificity of CA19-9 at a cutoff of 20 U/ml was similar to that of CEA at a cutoff of 5.0 ng/ml; CA19-9 was more sensitive than CEA in pancreatic cancer, whereas CEA was more sensitive than CA19-9 in breast, colon, and gastric cancer. Of 17 patients with pancreatic cancer, 13 had elevated levels of CA19-9 (sensitivity, 76%), whereas only 8 had elevated levels of CEA (sensitivity, 47%) and 15 had elevated levels of either CEA or CA19-9 (sensitivity, 88%). These findings suggest that, like CEA, CA19-9 is detectable in nonmalignant diseases and is not specific for gastrointestinal tumors, and has higher sensitivity than CEA only in pancreatic cancer. However, further prospective studies are required to verify its value in the diagnosis and management of pancreatic cancer.