Bilateral preventive mastectomy may reduce breast cancer risk by more than 90 percent in women with BRCA1 or BRCA2 mutations, and it may be even more effective with oophorectomy, according to an article published online February 23rd by the Journal of Clinical Oncology.

Researchers had already recommended that women with the mutations undergo oophorectomy at the completion of child bearing based on studies showing that the procedure reduces ovarian cancer risk by at least 90 percent. Now physicians can add that bilateral preventive mastectomy dramatically reduces breast cancer risk and that the risk reduction may be even higher when mastectomy follows or is done in conjunction with oophorectomy.

The current study was the first to calculate risk reduction from bilateral mastectomy in BRCA1 and BRCA2 mutation carriers; the trial involved 483 women from 11 sites in the United States, Canada, United Kingdom, and the Netherlands over 6 years. Of 105 women who underwent preventive mastectomy, 2 (1.9 percent) were diagnosed with breast cancer, compared with diagnosis in 184 of 378 women (48.7 percent) who did not undergo preventive surgery.

Mastectomy reduced breast cancer risk by approximately 95 percent in women with prior or concurrent preventive oophorectomy, compared with risk reduction of 90 percent in women with intact ovaries.

“Our study shows that bilateral prophylactic mastectomy markedly reduces the risk of breast cancer in women who are genetically predisposed to the disease,” said Barbara Weber, MD, senior author of the study. “Women undergoing this procedure should feel confident that if they choose this risk management option, it will reduce their risk of breast cancer to almost zero.”

Weber noted that while bilateral mastectomy is optional for BRCA1 and BRCA2 mutation carriers, bilateral preventive oophorectomy at the completion of childbirth should be standard care because it has been shown to reduce risk of ovarian cancer by 95 percent and breast cancer by 50 percent.