Exemestane Prevents Breast Cancers in Postmenopausal Women


A daily dose of the aromatase inhibitor exemestane dosage reduced invasive breast cancers by 65% in a placebo-controlled chemoprevention trial that enrolled 4,560 postmenopausal women considered at increased risk of the disease.

Pre-invasive breast cancers and precancerous lesions also were much less common at a median follow-up of 3 years in the study, which is expected to reopen a stalled conversation between women and their physicians regarding the risks and benefits of chemoprevention.
Two selective estrogen receptor modulator (SERM) drugs – tamoxifen and raloxifene (Evista) – are approved for breast cancer prevention, but they are little used for that purpose. Estimated tamoxifen use runs as low as 4% in high-risk women, who are thought to be deterred by rare but potentially serious side effects.

Exemestane (Aromasin) could become a third option for breast cancer prevention in postmenopausal women, Paul E. Goss, M.D., Ph.D., the lead author, said, announcing the results on behalf of the MAP.3 (Mammary Prevention.3 trial) investigators at the annual meeting of the American Society of Clinical Oncology.

"Because of the significant reduction of breast cancer and the excellent safety profile, exemestane has the potential for wider-scale implementation than the selective estrogen modulators in our view," declared Dr. Goss, a professor of medicine at Harvard Medical School and Massachusetts General Hospital in Boston.

Women had to be age 35 or older and postmenopausal with at least one specified risk factor to enter the trial, he noted. Age greater than or equal to 60 years by itself was considered a risk factor, as were a five-year Gail risk score greater than 1.66%, prior atypical ductal or lobular hyperplasia or lobular carcinoma in situ, or prior ductal carcinoma in situ with prior mastectomy.