Role of tamoxifen in the long-term treatment and prevention of breast cancer.

The past twenty years have witnessed the introduction and development of antiestrogens as powerful new nontoxic drugs for the treatment of breast cancer. Tamoxifen is currently the agent of choice for the endocrine treatment of breast cancer. Several clinical studies now support the concept that long-term or indefinite adjuvant tamoxifen therapy is of benefit to at least some groups of Stage I/II breast cancer patients (usually those who are estrogen receptor positive). This article will consider the basic laboratory principles that led to the successful clinical testing of long-term adjuvant tamoxifen therapy; future strategies to improve the encouraging early results of long-term antiestrogen therapy will be offered and the use of antiestrogens as a possible preventive in women at high risk for breast cancer will be considered.