Recent advances in endocrine therapy for postmenopausal women with early breast cancer: implications for treatment and prevention.

BACKGROUND In the treatment of advanced breast cancer, third-generation aromatase inhibitors (AIs) have shown superior efficacy and tolerability compared with tamoxifen and megestrol acetate, the previous standard endocrine therapies in the first- and second-line settings, respectively. AIs are now being assessed in the adjuvant and prevention settings. DESIGN Literature review (PubMed search). RESULTS Tamoxifen is currently the only endocrine option available for adjuvant therapy and chemoprevention in postmenopausal women. However, results from the ATAC ('Arimidex', Tamoxifen, Alone or in Combination) trial have shown anastrozole to be more effective than tamoxifen as adjuvant therapy for postmenopausal women with hormone-responsive early breast cancer. Other third-generation AIs, including letrozole and exemestane, are also being investigated as adjuvant therapies. In the chemoprevention setting, tamoxifen is the only available endocrine option for women at high risk of breast cancer but, given that these are healthy subjects, is associated with an unacceptable rate of adverse events. Raloxifene is being further assessed in the STAR (Study of Tamoxifen and Raloxifene) trial, while anastrozole is being evaluated in the second IBIS-II (International Breast Intervention Study II). CONCLUSIONS AIs, in particular anastrozole, are set to change the way that early breast cancer is treated. Effective and better-tolerated endocrine alternatives for breast cancer prevention may become available in the future.