Clinical evaluation of a new tumor marker, CA 15-3, in breast cancer; a comparative study with CEA

Recently, a new RIA method has been developed by Centocor Co., utilizing the monoclonal antibody CA 15-3. We performed a clinical trial to evaluate its utility as a tumor marker for breast cancer in comparison with CEA. We set 15 U/ml as the cut-off value of serum CA 15-3 level from results acquired from controls; 10 volunteers and 17 patients with non-malignant diseases. The CA 15-3 positive rate among the cases of primary breast cancer was 13.3%, which was of poor diagnostic value. In the recurrent cases the positive rate of CA 15-3 was 72.0%, which was valuable compared with that of serum CEA, 52.0%. In the cases of primary cancers other than breast cancer, the positive rate of CA 15-3 was 6.9%.