Treatment of disease-negative but mucin-like carcinoma-associated antigen-positive breast cancer patients with tamoxifen: preliminary results of a prospective controlled randomized trial.

Increasing levels of tumor markers such as carcinoembryonic antigen, mucin-like carcinoma-associated antigen (MCA), CA 15.3, and monoclonal antibody H23 in breast cancer patients following the treatment of the primary disease and adjuvant radiation and chemotherapy reflect subclinical development of metastatic disease. Overt metastatic disease is usually incurable and prolongation of life at this stage is impossible, and the treatment is only palliative. The efficacy of tamoxifen, a least-toxic agent, in the treatment of early and minimal metastatic disease detected only by increasing serum levels of MCA was studied prospectively in a randomized study. Our preliminary, albeit encouraging, results showed that the rate of relapse within a median follow-up period of 11 months was 24.1% in the control arm as compared with 0% in the tamoxifen arm (Fisher's exact test, P = 0.012). None of the patients with a relapse had positive progesterone receptors (PR). We may carefully conclude that early treatment may be warranted in young patients with negative PR and continuously increasing serum levels of the marker.