The Aromatase Inhibitors as Adjuvant Therapy for Hormone Receptor-Positive Breast Cancer

Adjuvant hormonal therapy has been shown to decrease the risk of breast cancer recurrence and overall mortality in patients with hormone receptor-positive breast cancer. Tamoxifen has been used in this setting for many years, both in premenopausal and postmenopausal patients. Tamoxifen is not devoid of toxicity, and attempts have been made to develop newer hormonal agents with better efficacy and less toxicity. The aromatase inhibitors have shown equivalent or superior efficacy to tamoxifen in the treatment of metastatic breast cancer, and efforts are underway to determine the role of these agents in early breast cancer. The ATAC trial recently showed that use of the third-generation aromatase inhibitor anastrozole in the adjuvant setting led to a modest improvement in relapse-free survival as compared with tamoxifen. Patients treated with anastrozole were also less likely to develop uterine cancer or experience a thromboembolic event. However, patients treated with anastrozole were more likely than those treated with tamoxifen to suffer a fracture or other musculosketal problem. An ASCO technology assessment panel reviewed the relevant data and issued a consensus statement regarding the use of aromatase inhibitors in the adjuvant setting. In general, the panel favored the continued use of tamoxifen as adjuvant hormonal therapy for most postmenopausal women. Within the next few years, further data from the ATAC trial and from other trials of aromatase inhibitors in the adjuvant setting should be available to guide treatment recommendations for this patient population.