Effect of tamoxifen on immune functions.

Tamoxifen (20 mg twice daily) was given to ten patients with breast cancer whose immune functions were determined prior to and 3, 6, and 12 months after starting tamoxifen therapy. No consistent changes could be observed in erythrocyte rosette-forming cell counts, erythrocyte antibody rosette-forming cells, active erythrocyte rosette-forming cells, theophylline-resistant rosette-forming cells, surface immunoglobulin-positive cells, and responses to mitogens phytohemagglutinin and concanavalin A. Erythrocyte antibody rosette-forming cells decreased significantly, however, at 6 months and active erythrocyte rosette-forming cells at 12 months after starting tamoxifen. We conclude that no change in the immune capacity could be detected during tamoxifen treatment.