Prescribing extended adjuvant letrozole

The efficacy of 5 years of adjuvant tamoxifen in preventing disease recurrence in patients with breast cancer has been well established. Once patients have completed tamoxifen therapy, however, recurrence risk remains but treatment options are limited. Aromatase inhibitors such as letrozole are emerging as potential alternatives to tamoxifen therapy and as an option after tamoxifen. The pioneering MA-17 trial was designed to evaluate the efficacy and safety of letrozole in the extended adjuvant setting in postmenopausal women who remained disease-free after about 5 years of tamoxifen. The trial was unblinded at first interim analysis after letrozole proved more effective than placebo in improving disease-free survival. As such, the optimal duration of extended adjuvant letrozole was left in question. However, recent results from cohort analysis in MA-17 have shown an ongoing and increasing benefit of letrozole for up to 4 years after tamoxifen, suggesting that longer periods of extended adjuvant letrozole are safe and clinically beneficial.