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Ovary removal does not protect BRCA1 mutation carriers against breast cancer, study finds

December 2016

WCH scientists reevaluate oophorectomy in breast cancer prevention

Ovary-removal surgery, or oophorectomy, does not reduce the risk of breast cancer for most women with a BRCA1 or BRCA2 genetic mutation as much as previously thought, a new study by scientists at Women’s College Hospital (WCH) has found. However, the surgery may reduce risk for BRCA2 carriers under the age of 50.

The findings, published Sept. 6 in the Journal of the National Cancer Institute, reinforce the recommendation that women with a BRCA1 or BRCA2 mutation should consider preventive mastectomy. Scientist Joanne Kotsopoulos, PhD, and senior author Dr. Steven Narod, the director of the familial cancer research group at WCH and a Tier 1 Canada Research Chair in Breast Cancer, conducted the study.

“Our findings show that oophorectomy does not protect against breast cancer for BRCA1 mutation carriers,” said Kotsopoulos. “We did see a protective effect for BRCA2 mutation carriers diagnosed before age 50. However, this requires further confirmation.” Tumours in BRCA2 carriers are more sensitive to sex hormones produced within the ovaries, which could account for why younger BRCA2 carriers were protected.

Previously, surgery to remove both the ovaries and fallopian tubes was thought to reduce the risk of breast cancer by up to 50 per cent. “This reminds us that it is important to re-evaluate the role of known risk factors for hereditary cancer through large, long-term studies of many women,” Kotsopoulos said.

The study is the largest analysis of its kind. Scientists recruited 3,722 women from around the world with a BRCA1 or BRCA2 mutation and no history of cancer. They used follow-up surveys over several years to track oophorectomies and breast cancer diagnoses.

“It is important for women to understand their risk of breast cancer and the options available to them. Preventive mastectomy is highly effective at preventing breast cancer and recommended to women with a BRCA mutation,” Dr. Narod said. “We are also investigating new prevention options for BRCA mutation carriers that may save more lives without resorting to surgery.”

The authors reiterate that they still recommend oophorectomy for high-risk women at age 35 if they carry a BRCA1 mutation and age 40 if they carry a BRCA2 mutation. Previous studies have shown that oophorectomy reduces the risk of ovarian, fallopian and peritoneal cancer by 80 per cent and reduces the risk of death from all causes.

Joanne Kotsopoulos, PhD, and Dr. Steven Narod
Joanne Kotsopoulos, PhD, and Dr. Steven Narod at WCH.

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