Clinical evaluation of an immunoradiometric assay for CA15-3 antigen associated with human mammary carcinomas: comparison with carcinoembryonic antigen.

Serum levels of CA15-3, a mammary tumor associated antigen recognized by two different murine monoclonal antibodies (115D8 and DF3), were investigated in patients with mammary carcinoma and other benign or malignant diseases. The reference value of the serum CA15-3 level was obtained as 24 units/ml at the 99% confidence limit among healthy individuals (n = 462). Elevation of serum CA15-3 levels was observed in 24.3% of overall patients with mammary carcinoma. Serum CA15-3 levels in breast cancer patients correlated with the clinical stage; higher percentages of positivity were observed in those with advanced breast cancer (stage IV, 64.7%, recurrent, 52.4% and metastatic, 70.3%). Furthermore, elevated serum CA15-3 levels in breast cancer patients responded well to the effect of therapy. Although the serum CA15-3 test gave percentages of positivity of breast cancer similar to those found by the serum CEA test, the serum CA15-3 test revealed lower percentages of positivity than the serum CEA test among patients with benign breast lesions, liver cirrhosis or other carcinomas. These results suggest that the serum CA15-3 antigen level provides a very useful marker for diagnosis and clinical monitoring of patients with breast cancer.