ASCO: Exemestane Lowers Invasive Breast Cancer Risk

Drug not associated with serious toxic effects in postmenopausal women

MONDAY, June 6 (HealthDay News) -- Exemestane appears to reduce the risk of invasive breast cancers in postmenopausal women at an elevated risk of breast cancer, without serious adverse events, according to a study published online June 4 in the New England Journal of Medicine to coincide with the annual meeting of the American Society of Clinical Oncology, held from June 3 to 7 in Chicago.

Paul E. Goss, M.D., Ph.D., of the Massachusetts General Hospital Cancer Center in Boston, and colleagues randomized 4,560 women (median age, 62.5) to receive exemestane or placebo. The women had at least one of these risk factors: aged 60 or older, Gail five-year risk score above 1.66 percent, previous atypical ductal or lobular hyperplasia or lobular carcinoma in situ, or ductal carcinoma in situ with mastectomy.

After a median follow-up of 35 months, the investigators found 11 invasive breast cancers among those given exemestane and 32 in those who received placebo, with a 65 percent relative reduction in the annual incidence of invasive breast cancer in those given exemestane. The annual incidence of invasive plus noninvasive (ductal carcinoma in situ) breast cancers was lower in those who received exemestane as compared to those who received placebo (0.35 versus 0.77 percent; hazard ratio, 0.47). The investigators found no significant differences in adverse events between the two groups in terms of skeletal fractures, cardiovascular events, other cancers, or treatment-related deaths.

"Exemestane significantly reduced invasive breast cancers in postmenopausal women who were at moderately increased risk for breast cancer," the authors write. "During a median follow-up period of three years, exemestane was associated with no serious toxic effects and only minimal changes in health-related quality of life."

The study was supported in part by Pfizer; several authors disclosed financial ties to Pfizer and other pharmaceutical companies. The study also received support from the Avon Foundation.

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