Are all aromatase inhibitors the same?: A review of the current evidence

Third-generation aromatase inhibitors (Als)-letrozole, anastrozole, and exemestane-are challenging tamoxifen as the standard endocrine therapy for postmenopausal women with hormone receptor-positive breast cancer. Als suppress estrogen Levels by inhibiting aromatase, the enzyme that catalyzes the final step of estrogen biosynthesis. Studies have shown that Als are highly effective and safe in the treatment of advanced disease, and more recently, Als have shown promise in the neoadjuvant, adjuvant, and extended adjuvant settings. However, all Als are not equal. In direct comparisons with anastrozole, letrozole has demonstrated superior estrogen suppression and clinical response in patients with advanced metastatic breast cancer. In addition, letrozole is the only Al to demonstrate consistent superiority over tamoxifen in the neoadjuvant and first-line advanced breast cancer settings. This publication summarizes the available evidence for the efficacy of all 3 agents throughout the breast cancer continuum. (C) 2004 Published by Elsevier Ltd.