Double mastectomy can reduce death risk for some breast cancers by 50 per cent

Women with BRCA-related breast cancer can halve their risk of dying from breast cancer with a double mastectomy, according to a U of T-led study published in the British Medical Journal.

The study led by Professor Kelly Metcalfe, from U of T's Lawrence S. Bloomberg Faculty of Nursing, reported that women 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.

Many media reports on the study have noted its connection to Angelina Jolie's highly publicized and controversial decision to undergo a preventative double-mastectomy last year. (Read a U of T News interview with Professor Metcalfe about Angelina Jolie's preventative surgery) 

Metcalfe explained this breakthrough research and how the study findings have the potential to change the future of breast cancer treatment.

What did your study show?
What we saw is that women with a BRCA genetic mutation who had a bilateral mastectomy – that is, had both breasts removed – had half the chance of dying from breast cancer compared to women who had just one breast removed. At 20 years, the survival rate was 88 per cent for the women who had a double mastectomy, but only 66 per cent for women having a single mastectomy.

In the study, we assessed the medical records of 390 women across North America who had been diagnosed with early-stage breast cancer, had a BRCA mutation, and had been treated with either a single or double mastectomy. We followed the women, on average, for 14 years after their initial diagnosis. 

We know that women with a BRCA1 or BRCA2 mutation and who have been diagnosed with breast cancer have a high lifetime risk of developing a subsequent cancer in the same or opposite breast. However, we didn’t know what impact a diagnosis of a second breast cancer had on mortality. This study has shown that women who develop a second breast cancer have twice the risk of dying of their disease. So when we think of treating a woman with a BRCA mutation, we need to think not just about treating her first breast cancer, but preventing a second breast cancer.

Our research may change the way we think about treating women with BRCA-associated breast cancer. These women may need a different surgical treatment than those without the genetic mutation; for them, a more conservative surgery may be appropriate.

Can your research findings be put into practice?
Yes, they can immediately go into clinical practice. We need to prevent this cohort of women from getting a second breast cancer, and the way to prevent that second breast cancer is a bilateral mastectomy.

It’s important for women to be aware of these study findings because it shows that there may be a survival benefit associated with having a bilateral mastectomy. To translate this information into clinical practice, though, a woman needs to know if she has BRCA mutation.

Should BRCA testing be offered more readily?
I think so. BRCA testing is not appropriate for every woman, but it is appropriate for women with young-onset breast cancer, women with a strong family history of the disease, and women who are Jewish, as there’s a higher frequency of these mutations in the Jewish population.

This research speaks to the importance of a woman being offered genetic testing at the time of breast cancer diagnosis and receiving those results quickly. In the era of personalized medicine, it is important that a woman has this genetic information, so her breast cancer treatment can be targeted to obtain the best possible outcome.

With this information, will women elect to have a bilateral mastectomy?
That’s what we’re evaluating now. We don’t want to cause more distress to a woman at the time of breast cancer diagnosis. We want to make sure that it’s appropriate to give women this information and also that they do something with the knowledge. If the information doesn’t impact treatment decisions, it may not be necessary to do genetic testing at diagnosis.    

Susan Pedwell is the editor of Pulse, U of T Nursing’s biannual magazine.