Antiestrogen therapy for breast cancer: current strategies and future prospects.

The antiestrogen tamoxifen has had an enormous impact upon the therapy of breast cancer. It is the most widely used antihormonal therapy. The success of tamoxifen has stimulated broader applications of the drug (long-term adjuvant therapy and chemosuppression) and has spurred the development of toremifene, droloxifene, and zindoxifene. However, the clinical evaluation of tamoxifen as a chemosuppressive agent is not sufficiently advanced to be able to provide any conclusion about the success of this strategy. It may be a decade before a randomized clinical study can be analyzed and the value of chemosuppression assessed. In the near future, the clinical evaluation of new antiestrogens will provide additional information about the potential value of these drugs and will perhaps challenge our ideas about the mode of action of antiestrogens as antitumor agents.