New Developments in Endocrine Therapy

Tamoxifen has become the standard of care in relation to hormonal therapy for women with hormone-sensitive tumors. However, recently completed and ongoing studies indicate that third-generation aromatase inhibitors may be more effective than tamoxifen for a wide range of patients with breast cancer. Drugs in this class currently are approved as first-line endocrine therapy for postmenopausal women with metastatic hormone-dependent breast cancer, and as second-line endocrine therapy after failure of antiestrogen therapy alone or multiple hormonal therapies. The interim results from the Arimidex, Tamoxifen Alone or in Combination Trial support the use of an aromatase inhibitor as an alternative to tamoxifen for adjuvant therapy in postmenopausal women with operable breast cancer that is hormone positive. In this trial, anastrozole had a favorable side effect profile, with fewer cases of endometrial cancer and fewer thromboembolic events than tamoxifen. Other recent studies have indicated that an aromatase inhibitor may be superior to tamoxifen as preoperative treatment for women with hormone-sensitive, primary breast cancer. Numerous clinical trials currently are comparing the efficacy of aromatase inhibitors with that of tamoxifen used as adjuvant therapy for postmenopausal women who have early-stage breast cancer. The results of these trials will provide additional information about the best ways to use these powerful agents for patients with breast cancer.