TAG-72 (CA 72-4 assay) as a complementary serum tumor antigen to carcinoembryonic antigen in monitoring patients with colorectal cancer

Background. Serum carcinoembryonic antigen (CEA) is the most frequently chosen tumor marker in the clinical diagnosis of colorectal carcinoma and in the long-term monitoring of patients after tumor resection. In recent years, monoclonal antibody technology has identified several new markers of neoplasia, two of which, TAG-72 and CA 19-9, are found in the sera of patients with adenocarcinoma. Serum CEA, TAG-72, and CA 19-9 were evaluated in 300 patients with either malignant (n = 200) or benign (n = 100) colorectal disease. Methods. Serum CEA, TAG-72 (CA 72-4), and CA 19-9 antigen levels were determined with a double-determinant radioimmunometric assay kit. Samples and appropriate standards were assayed in duplicate. The cutoff limits used for each assay were indicated by the manufacturer. All of the results of the CA 72-4, CEA, and CA 19-9 serum assays were separated from the clinical information until the study was completed. Results. Of the 200 patients with colorectal carcinoma, the percentage of patients whose serum samples were positive for CEA, TAG-72, or CA 19-9 was 43%, 43%, and 27%, respectively. The measurement of TAG-72 with CEA for patients with primary or recurrent colorectal carcinoma increased substantially (to 60%) the percentage of positive serum samples when compared with measuring each serum tumor marker alone. Moreover, the apparent advantage gained by measuring the two tumor markers was achieved with little increase in the number of false- positive results. Conclusions. The findings support previous observations of complementary expression of TAG-72 and CEA and indicate that a significant advantage could be gained in the detection of primary and, perhaps, recurrent colorectal carcinoma by incorporating the measurement of serum TAG-72 with that of CEA.