The value of the tumor marker CA 15-3 in diagnosing and monitoring breast cancer. A comparative study with carcinoembryonic antigen.

To estimate the utility of the tumor-associated antigen CA 15-3 in the diagnosis of patients with breast cancer, this tumor marker was measured preoperatively in 1342 patients. This group included 509 patients with malignant disease (134 breast cancer patients and 375 patients with other malignancies not involving the breast) and 833 patients with benign surgical diseases (95 patients with fibroadenoma of the breast and 738 patients with other benign diseases). The results were compared with those obtained for carcinoembryonic antigen (CEA) in the diagnosis of breast cancer. The CA 15-3 level was above normal (25 U/ml) in 31% of the patients with breast cancer, in 22% of patients with other malignancies, and in 9% of patients with benign diseases. The CEA level was elevated in 26% of patients with breast cancer (more than 3 ng/ml). There was a good correlation of CA 15-3 levels with the tumor stage of breast cancer. Both CA 15-3 and CEA also were determined in 671 patients who had received initial curative surgery of breast cancer and who regularly attended our follow-up clinic. The CA 15-3 was found to be more sensitive than CEA in detecting recurrences of breast cancer. In the postcare period, carcinoma recurred in 205 patients. Of these, 73% had CA 15-3 concentrations above 25 U/ml; only 50% had CEA values above 3 ng/ml (P less than 0.0001). Although neither CA 15-3 nor CEA were sensitive enough for the screening and diagnosis of early breast cancer, CA 15-3 was significantly better than CEA in the detection of breast cancer metastases.