Exemestane for Breast Cancer Risk Reduction

Abstract

SUMMARY Chemoprevention of estrogen receptor (ER)-positive invasive breast cancers is a feasible maneuver with the use of the selective ER modulators tamoxifen and raloxifene. However, their uptake as chemoprevention agents has remained low, mainly due to concerns about toxicity, and specifically the risk of thromboembolism and endometrial carcinomas. Aromatase inhibitors have not been associated with these potentially serious complications. Exemestane is a steroidal aromatase inhibitor recently studied in the randomized MAP.3 trial for breast cancer chemoprevention in a high-risk population. After 3 years of follow-up, the incidence of invasive breast cancer was reduced by 65% and the incidence of ER-positive invasive breast cancers by 73%. The risk of osteoporosis and cardiovascular events was not higher with exemestane. Longer follow-up is warranted, but exemestane can be considered an option for the chemoprevention of breast cancer in a high-risk postmenopausal female population.