Prospective evaluation of the diagnostic efficacy of CA 19-9 assay as a marker for gastrointestinal cancers.

Levels of a new carbohydrate antigen, CA 19-9, which is a monosialoganglioside identified by a monoclonal antibody raised against colorectal carcinoma cells, were compared to conventional CEA assays in 615 sera from healthy controls, patients with benign gastrointestinal disorders, and patients with cancers of gastrointestinal or extragastrointestinal origin. Whereas CEA levels were higher in smokers, CA 19-9 values were independent of the smoking history. CA 19-9 was undetectable in lymphoma and myeloma patients, but some patients with extraintestinal epithelial cancers expressed this antigen in serum. For benign and malignant gastrointestinal diseases, CA 19-9 displayed higher sensitivity, specificity, and predictive values than CEA. CA 19-9 was elevated as frequently as CEA in patients with metastatic pancreatic cancer, but in patients with localized disease, CA 19-9 was elevated more often than was CEA. In colorectal cancer, patients with and without metastases were detected at similar rates by both assays. It is concluded that CA 19-9 is a marker of epithelial cancers, does not vary with the smoking status, and is superior to CEA in detecting gastrointestinal malignancies, especially those arising from the pancreatic gland.