Emerging Data on Optimal Adjuvant Endocrine Therapy: Breast International Group Trial 1-98/MA.17

In recent years, several major trials have studied aromatase inhibitors (AIs)/inactivators as adjuvant therapy for postmenopausal women with early-stage breast cancer. The AIs have demonstrated improved efficacy compared with 5 years of tamoxifen when used as initial therapy or when used sequentially after 2-3 years. They also improve outcomes when used after 5 years of adjuvant tamoxifen in this patient population. In all cases, AIs improve disease-free survival compared with the standard 5 years of adjuvant tamoxifen, leading to a reassessment of the optimal adjuvant endocrine therapy for postmenopausal patients with breast cancer. The American Society of Clinical Oncology now recommends the inclusion of an AI into the adjuvant regimen at some point for most postmenopausal patients with hormone receptor—positive earlystage breast cancer. However, the optimal duration of AI therapy and the comparative efficacy and safety of the alternative strategies for their incorporation remain matters of debate. In addition, the long-term impact of AIs on other organs, such as the bone and cardiovascular systems, is not completely understood, and longer follow-up of patients from these original trials as well as carefully planned future trials with appropriate substudies are essential to determine the optimal endocrine treatment strategy.