Postmenopausal women with hormone receptor-positive breast cancer: balancing benefit and toxicity from aromatase inhibitors.

Extensive clinical trial experience is available for aromatase inhibitors (AIs) in postmenopausal women upon which to evaluate the balance of potential benefit and toxicities. A meta-analysis revealed an advantage for AIs over tamoxifen in the monotherapy setting for recurrence but not breast cancer mortality, and an advantage in both of these parameters for switching to an AI after several years of tamoxifen. Importantly, no indication of a deleterious effect of AIs was identified in terms of death without recurrence in these meta-analyses. Regarding serious adverse events (AEs), there are data indicating an increase in cardiovascular AEs and bone fractures but a lower incidence of thromboembolic phenomena and endometrial cancer with AIs vis-à-vis tamoxifen. There does not appear to be a difference in cerebrovascular AEs. Musculoskeletal AEs are the most common clinically important AEs as they are the most common cause of discontinuation of therapy, which can have an adverse effect on outcomes. The balance of benefit and toxicity favors the use of AIs in the adjuvant setting but the absolute benefit from AIs can be decreased in patients with advancing age or increasing comorbidities.