Women at high risk of breast and ovarian cancer due to BRCA1 and BRCA2 gene mutations substantially reduce their chances of developing the disease with preventive surgery, a major study lead by University of Pennsylvania researchers.

The study, which confirms and expands previous findings, followed 2,482 women with the gene mutations. The objective of the study in Wednesday’s issue of the Journal of the American Medical Association was to estimate the risk reduction of undergoing preemptive mastectomies or removal of the ovaries and fallopian tubes.

The BRCA gene mutations increase the life-time risk of breast and ovarian cancers. Breast cancer risk for women with the mutations was 56 percent to 84 percent. The risk of ovarian cancer for those with the BRCA1 mutation is estimated to be 36 percent to 63 percent, and between 10 percent and 27 percent for those with the BRCA2 mutation.

After three years none of the 247 women who underwent risk-reducing mastectomies developed breast cancer compared with 98, or 7 percent, of the 1,372 who opted for aggressive cancer surveillance. Moreover, significantly fewer women (including those with previous cancer diagnoses) developed ovarian cancer after undergoing salpingo-oophorectomies – the surgical removal of their ovaries and fallopian tubes.

“Compared with women who did not undergo risk-reducing salpingo-oophorectomy, undergoing salpingo-oophorectomy was associated with lower all-cause mortality (10 percent vs. 3 percent), breast cancer-specific mortality (6 percent vs. 2 percent), and ovarian cancer-specific mortality (3 percent vs. 0.4 percent),” wrote the authors, led by Penn’s Susan M. Domchek.

Penn’s Timothy R. Rebbeck was the study’s senior author and Mary B. Daly from the Fox Chase Cancer Center also participated, as did doctors and researchers from 20 other leading cancer treatment and research institutions across the country.

An editorial that accompanied the study in JAMA noted that the study “demonstrates prophylactic surgery for high-risk women not only reduced the risk of developing cancer, but is also associated with decreased mortality.”

The editorial emphasized the importance of early detection of the gene mutations for women. “Early identification of BRCA1 or BRCA2 mutation status empowers women to better understand their risk and make choices about screening and prophylaxis that are consistent with their values.”

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