Women at highest risk for breast cancer benefit most from preventive therapy

Women at the highest risk of contracting breast cancer benefit the most from preventive drug therapy, including tamoxifen and raloxifene, according to a study, published in the April 16, 2013, issue of the Annals of Internal Medicine.

The study was conducted by the United States Preventive Services Task Force (USPSTF) and was led by Heidi D. Nelson, MD, MPH, with the Pacific Northwest Evidence-based Practice Center at Oregon Health & Science University.

In 2002, the USPSTF recommended against routine use of tamoxifen and raloxifene for prevention of breast cancer for women at average risk. The new data will inform an upcoming recommendation statement from the USPSTF.

After analyzing MEDLINE and Cochrane databases from 2007 through December 2012, researchers found that women who received tamoxifen, raloxifene, or exemestane had a 10-year breast cancer risk of 7.5% compared with a 21.3% risk for women on no treatment.

Tamoxifen and raloxifene reduced the incidence of invasive breast cancer and breast cancer in placebo-controlled studies, the researchers found. While tamoxifen had greater effect at reducing invasive breast cancer than raloxifene, the drug produced more thromboembolic events, endometrial cancer, related gynecologic outcomes, and cataracts.

“Many women have less serious adverse effects [from both tamoxifen and raloxifene] that impact quality of life and adherence, such as vasomotor, genital, and musculoskeletal symptoms,” Dr Nelson wrote in the Annals of Internal Medicine study. In trials, older women had more adverse effects for some outcomes, such as endometrial cancer and thromboembolic events, than women younger than aged 50 years.

Despite previous recommendations to identify women at increased risk for breast cancer and offer risk-reducing medications, this practice is uncommon in the United States, the researchers found. “It is not clear how to identify candidates for therapy,” Dr Nelson wrote. “Although the trials indicate broad benefit, subgroup analysis and decision models suggest that high-risk women, particularly those who had hysterectomies, may derive the most benefit with the least harms,” she added.