The Value of New Tumor Marker CA 15-3 in Diagnosis and Monitoring of Patients with Breast Cancer

Serum levels of a tumor-associated antigen, designated CA 15-3, which is defined by two monoclonal antibodies, in 60 untreated breast cancer patients in various stages were determined by immunoradiometric assay. CA 15-3 levels were found to be higher than maximum level of normal control subjects (27 u/ml), in 38,4% of cases in clinical stage-11, 40% of cases in stage-III and 75% of cases in stage-IV. In order to evaluate the correlation between the clinical course and CA 15-3 levels, serial measurements were performed in 32 patients. CA 15-3 levels were lower than initial values in 75% of cases with clinical, radiological, laboratory regression, on the other hand in 87% of cases with progressive disease, CA 15-3 levels were found to be elevated. These observations indicate that CA 15-3 is a sensitive tumor marker for diagnosis and especially for monitoring of breast cancer patients.