Aromatase inhibitors (AIs) are becoming more widely used than
tamoxifen as adjuvant hormonal
therapy for postmenopausal women (PMW) with early
breast cancer (EBC). It is clear that these drugs offer important efficacy benefits over
tamoxifen and differ from
tamoxifen in their safety profile. The accepted strategies for adjuvant AI
therapy include initial adjuvant treatment following surgery, switching and/or sequencing from prior
tamoxifen, and extended adjuvant
therapy following the full 5 years of
tamoxifen treatment. Among the available AIs,
letrozole has been evaluated in large, well-controlled, double-blind clinical trials in the initial adjuvant, extended adjuvant, and more recently, the sequential adjuvant settings.
Letrozole is the most potent of the AIs and provides near complete suppression of plasma
estrogens in PMW.
Letrozole also significantly reduces the occurrence of early distant
metastases, the most lethal type of recurrence event, which can lead to improved survival. Clinical comparisons of
letrozole with both
tamoxifen and placebo have also provided important long-term safety data on the use of AIs as adjuvant
therapy in PMW with EBC. The weight of clinical evidence indicates that
letrozole is a safe and effective option for adjuvant hormonal
therapy across all three AI treatment settings.