Safety of Adjuvant Endocrine Therapy in Postmenopausal Women With Breast Cancer

Abstract

The use of aromatase inhibitors (AIs) as adjuvant endocrine therapy for hormone-sensitive breast cancer is increasing, as these drugs are more effective than tamoxifen alone in improving disease-free survival in breast cancer patients-whether used in lieu of tamoxifen as upfront therapy or after tamoxifen treatment periods of 2 years or longer. AIs differ from tamoxifen in their mechanism of action, effectively suppressing estrogen levels in postmenopausal women to near-undetectable levels. AI-associated adverse events largely mimic menopausal symptoms, including hot flashes, losses in bone mineral density, gynecologic symptoms, and arthralgias. The AIs lack the infrequent but potentially serious adverse events associated with tamoxifen (eg, endometrial cancer, thromboembolic events, and stroke). Large randomized studies of AIs in the adjuvant setting have not demonstrated an adverse effect on lipids and cardiovascular health, but postmenopausal women receiving AIs are at risk for age-related changes in lipid parameters and an increased risk for cardiovascular events. To optimize the overall benefits of adjuvant endocrine therapy with an AI, patients should be monitored for bone loss and cardiovascular risk factors, and symptoms such as joint pain and vaginal dryness should be anticipated and managed proactively.