Breast cancer and BRCA mutations: Removing healthy breast saves lives

Women considering a mastectomy after being diagnosed with breast cancer often face a difficult decision: whether to remove their healthy breast as well.

A new study should make it easier for some of these women to make up their minds. It concludes that patients with a dangerous mutation in their BRCA1 or BRCA2 gene were able to cut their risk of dying from breast cancer nearly in half by opting to remove both breasts.

The BRCA1 and BRCA2 genes contain instructions for producing tumor suppressor proteins, which repair damaged DNA and keep cells from turning cancerous. But certain mutations in these genes prevent those proteins from doing their job. As a result, a woman with one of those mutations is estimated to have a 60% to 70% chance of developing breast cancer at some point in her life. (For women without these mutations, the average lifetime risk of breast cancer is 12.4%, according to the National Cancer Institute.)

Studies have found that in the U.S. and Canada, about half of women with a BRCA mutation who develop cancer in one breast opt to remove the other breast as well, in a procedure called a contralateral mastectomy. But researchers had not been able to show that this logical-seeming strategy worked as planned.

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So a team of investigators from the two countries examined the medical records of 390 women who had been diagnosed with Stage 1 or Stage 2 breast cancer between 1977 and 2009. All of the women had a confirmed high-risk mutation in one of their BRCA genes, or they were from a family that was known to carry the mutation and were presumed to have it too.

Among these 390 patients, 44 decided to remove both breasts at the same time, even though one of the breasts was cancer-free. Among the 346 who initially had a single mastectomy, 137 — or 40% — later opted to remove their remaining breast even though it was cancer-free. In these cases, the average gap between the two procedures was 2.3 years. (The researchers hypothesized that these women didn’t remove their second breast right away because didn’t yet know that they had a BRCA mutation.)

In the first decade after their initial surgery, there was no real difference in survival rates for the patients who removed both breasts compared to the patients who removed one. But in the second decade, the benefits became clear: Women who went ahead and removed their healthy breast were 80% less likely to die of breast cancer than women who only removed one breast.

Over the entire 20-year period of the study, 31% of the women who had only a single mastectomy died of breast cancer. However, the women who removed both breasts were 48% less likely to die of the disease. The results were published online Tuesday by the British Medical Journal.

The researchers shared a theory about why it took so long for the benefits of a contralateral mastectomy to kick in. Among the 209 women who only had a single mastectomy, 70 of them later developed a new breast cancer in their remaining breast, and 61 of them died as a result. The researchers calculated that these second cancers were more than twice as deadly as the initial cancers. Those second breast cancers take many years to arise, the researchers wrote.

The researchers advised doctors to recommend a contralateral mastectomy to their patients with early-stage breast cancer if they have a BRCA mutation. Even patients who have already had a single mastectomy should be informed of the benefits of double mastectomy, they added.

In many ways, the dilemma faced by these cancer patients is similar to the one that led Angelina Jolie to have a double mastectomy before cancer arose in either breast, according to an editorial that accompanies the study written by Karin Michels, an epidemiologist at Harvard Medical School who studies how epigenetics influence the risk of breast cancer.

For breast cancer patients with BRCA mutations who are considering a contralateral mastectomy, there’s only one question that matters, Michels wrote: “Will this reduce my risk of dying from breast cancer?” The new study suggests the answer is yes.

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