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Double mastectomy halves death risk for women with BRCA-related breast cancer

March 10, 2014

Dr. MetcalfeWomen with BRCA-related breast cancer who have a double mastectomy are nearly 50 per cent less likely to die of breast cancer within 20 years of diagnosis compared to women who have a single mastectomy, according to a new study led by Women’s College Hospital’s Kelly Metcalfe, PhD.

The findings, published in the British Medical Journal, suggest a double mastectomy may be an effective first-line treatment for women with early-stage breast cancer who carry a BRCA1 or BRCA2 genetic mutation. The BRCA1/2 genes belong to a class of genes that typically act to protect individuals from acquiring cancer, yet women who inherit a mutated form of the genes have a high risk of developing breast and ovarian cancers.

“Women with a BRCA mutation have a 60 to 70 per cent chance of developing breast cancer in their lifetime, and once diagnosed, a further 34 per cent chance of developing breast cancer in the opposite breast within 15 years,” said Metcalfe, an adjunct scientist at Women’s College Research Institute (WCRI) and professor at the University of Toronto. “For these women, we need to think about treating the first breast cancer, but also about preventing a second breast cancer.”

To compare the survival rates of women with BRCA-related breast cancers, researchers assessed the medical records of 390 women with stage one or two breast cancer and a BRCA1 or BRCA2 mutation. The women were required to have been initially treated with a single or double mastectomy. The researchers found:

  • Women who had a double mastectomy had a 48 per cent greater likelihood of surviving compared to women with a single mastectomy.
  • For women who developed a new breast cancer in the opposite breast, the risk of dying of breast cancer was doubled.
  • At 20 years, the survival rate was 88 per cent for women with a double mastectomy and 66 per cent for women with a single mastectomy.

“Our study’s results provide evidence that in order to improve survival in women with BRCA-associated breast cancer, we need to prevent new breast cancers from developing after an initial diagnosis,” said Dr. Steven Narod, a co-author of the study and a senior scientist at WCRI.  “This study highlights the importance of providing genetic testing for BRCA1 and BRCA2 at the time of breast cancer diagnosis if appropriate. This genetic information could help women make decisions that ultimately may increase their chance of surviving breast cancer.”

While existing research widely supports the benefit of a double mastectomy in preventing breast cancer in women with the gene mutation, the study’s researchers caution more research is necessary to confirm the benefit of a double mastectomy in reducing the risk of death in women diagnosed with BRCA-related breast cancer.

This research was funded by the Ontario region of the Canadian Breast Cancer Foundation.

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