Risk-reducing mastectomies (RRM) in women with a certain genetic variant may significantly reduce the risk of being diagnosed with breast cancer and lower the probability of death, a study has found.

The research, published in the British Journal of Cancer, examined how RRM -- a surgery to remove a breast -- affects the rate of death of women with a pathogenic variant but no cancer diagnosis.

"The decision to have a risk reducing mastectomy is often difficult for a woman to make, and the more evidence we are able to provide them with when they are making that decision, the more informed their care plan will be," said Professor Kelly Metcalfe from the University in Toronto, Canada.

Women who have an inherited BRCA1 or BRCA2 variant have an 80 per cent risk of developing breast cancer over the course of their lifetime, the researchers said.

Studies have shown that an RRM reduces the risk of breast cancer by 90 per cent, and in Canada, 30 per cent of women with a pathogenic variant opt for this surgery, they said.

It is one of the most effective ways of preventing breast cancer in women with this risk profile, Metcalfe said.

The researchers followed over 1600 participants from a registry of women with a pathogenic BRCA 1/2 variant from nine different countries over the course of six years, with half of the women having a risk-reducing mastectomy.

At the end of the trial, there were 20 incident breast cancers and two deaths in the group who opted for a RRM, and 100 incident breast cancers and seven deaths in the control group, the researchers said.

RRM reduced the risk of breast cancer by 80 per cent, and the probability of dying of breast cancer 15 years after risk-reducing mastectomy was less than one per cent, they said.

"Although there wasn't a significant difference in deaths between the two groups in this study, we know that a risk reducing mastectomy significantly reduces the risk of ever developing breast cancer," said Metcalfe.

Metcalfe noted that following these participants for an extended period would generate more evidence to assess the true mortality risk with precision and highlight the benefits associated with this type of surgery.

"Right now, we have good screening in place for breast cancer, including breast MRI, so surgery is only offered as an option, not a recommendation," Metcalfe said.

"But with more studies being conducted to assess women's trajectory and risk factors following RRM, we will know whether these guidelines need to be changed in the future," she added.

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