Value of serum levels of carcinoembryonic antigen, CEA, and gastrointestinal cancer antigen, GICA or CA 19-9, for preoperative staging and postoperative monitoring of patients with colorectal carcinoma.

Serum levels of gastrointestinal cancer antigen (GICA) and carcinoembryonic antigen (CEA) were determined in 167 patients with colorectal carcinoma. Eighty-eight patients were studied preoperatively, and 79 postoperatively, before, at the time of, and after the diagnosis of relapse. The authors aimed to assess how often the GICA test failed, i.e., was false-negative in patients in whom the CEA test was true-positive and, more importantly, whether it could give diagnostic information in patients in whom the CEA test failed. Before surgery, serum GICA gave similar information to serum CEA in 56 percent of the patients: true-positive in 18 percent and false-negative in 38 percent; less information in 42 percent; and more information in only 2 percent. During the postoperative follow-up, serum GICA gave similar information to serum CEA in 55 percent of the patients: true-positive (i.e., rising persistently from a postoperative nadir) in 27 percent and false-negative in 28 percent; less information in 44 percent; and more information in only 1 percent. Therefore, this test in its present version, where both the catcher and the tracer antibody are the same, NS 19-9, is redundant.