August 15th 2010
Each year in the United States, more than 200,000 women are diagnosed with breast cancer, and 40,000 women die of the disease. Approximately two-thirds of breast cancers are hormone receptor–positive, and medications that suppress estrogen are the cornerstone of adjuvant therapy for these tumors. Tamoxifen, a selective estrogen receptor modulator, was the first agent developed for this purpose and is still used widely in premenopausal women. Aromatase inhibitors (AIs), which prevent peripheral conversion of adrenal androgens into estrogen, have largely become the agents of choice for postmenopausal women. Current guidelines recommend that all postmenopausal women with hormone receptor–positive early-stage breast cancer who do not have a contraindication to AIs be treated with one of these agents, either as primary therapy or after 2 to 5 years of tamoxifen treatment as part of a cross-over strategy. These recommendations are based on five large adjuvant trials that demonstrated a 3% to 4% absolute reduction in subsequent breast cancer events in patients who received an AI as part of adjuvant breast cancer treatment compared with patients treated with 5 years of tamoxifen alone.[3-7] However, it is notable that despite the lower rates of recurrence in these trials in the patients who received AIs, most studies have not demonstrated a survival advantage for AIs.