Tamoxifen in the treatment of breast cancer.

Tamoxifen, an antiestrogen, is a competitive inhibitor of estradiol, blocking its effects on the target organs. During the 10 years it has been used in the United States it has become preferred over estrogens for treating postmenopausal women with metastatic breast cancer. Recently, tamoxifen has been used in treating premenopausal women with recurrent breast cancer, and its efficacy has been proved equal to that of ovarian ablation. In comparative trials, tamoxifen has been as effective as alternative endocrine treatments, and has greatly reduced toxicity and no irreversible side effects. Because of the high risk for systemic relapse in patients with breast cancer with regional lymph node metastases, (stage II), tamoxifen has been evaluated as adjuvant therapy after local treatment of the tumor. The results of these trials have shown a significant increase in the disease-free survival of postmenopausal women treated with tamoxifen, particularly in patients with hormone-receptor-positive tumors. Tamoxifen has not been as useful as adjuvant treatment in premenopausal women, for whom combination chemotherapy is the treatment of choice.