Serial serum MCA measurements in the follow-up of breast cancer patients.

Mucin-like carcinoma-associated antigen (MCA) was serially assayed in 58 women with histologically proven breast cancer after their treatment for primary disease. MCA sensitivity and specificity were 87.5% and 76.9%, respectively, and the positive predictive value 82.4%. 10 patients had elevated MCA and no evidence of disease (NED) during their follow-up, of whom 4 finally developed overt metastases. The 4 had a mean (S.D.) MCA value of 46.48 (18.26) U/ml during the lead time, versus 18.76 (2.69) U/ml in the other 6, who are still at high risk for developing overt metastases. Raised levels of MCA in patients with NED create a dilemma of "treat" versus "wait and see". Early treatment of patients with serially uprising MCA levels should be evaluated in a prospective randomised study to assess its ability to prevent or delay the development of overt metastatic disease and influence survival.