Adjuvant endocrine therapy is recommended to almost every woman with stage I to III breast cancer whose tumor expresses estrogen or progesterone receptors. Several strategies are available to women with early-stage, hormone receptor–positive breast cancer to improve disease-free survival (DFS) and overall survival, including tamoxifen for 5 to 10 years, aromatase inhibitors (AIs) for 5 to 10 years, or a sequential regimen of tamoxifen for 2 to 5 years followed by an AI for 3 or more years. Virtually every study that compared AI-based therapy with tamoxifen has demonstrated small DFS benefits to those receiving an AI.1-3 Therefore, the incorporation of an AI as part of their adjuvant endocrine therapy is recommended for postmenopausal women, and premenopausal women with high-risk, hormone receptor–positive tumors are considered for ovarian suppression with an AI.4-6