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Massachusetts General Hospital Cancer Center, Boston, MA, USA.
N Engl J Med 2011;364:2381–91.
Editor’s note: The acceptance of tamoxifen and raloxifene for reducing the risk of breast cancer has been poor, in part because both agents are associated with rare but serious toxic effects. In 2002, an assessment of the available data by experts concluded that tamoxifen lacked overall health benefits and recommended that future trials be conducted with placebo-receiving controls (J Clin Oncol 2002;20:3328–43). Aromatase inhibitors profoundly suppress estrogen levels in postmenopausal women and inhibit the development of breast cancer in laboratory models. Preclinical models and clinical studies have suggested that because of exemestane’s antiestrogenic effects, such as those on bone resorption resulting from its mild androgenic activity, it is a good candidate for study in a breast cancer prevention trial. In this article, the authors report the results of a randomized placebo-controlled double-blind trial of exemestane designed to detect a 65% relative reduction in the incidence of invasive breast cancer (IBC).