For some women with early stage breast cancer, removing the healthy breast likely doesn't afford much of a survival benefit, according to a new study.
"A lot of women with cancer in one breast decide to have both breasts removed to try to improve their survival or life expectancy," said senior author Dr. Todd M.Tuttle, a surgeon at the University of Minnesota in Minneapolis.
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For some women - such as those at high genetic risk for breast cancer - removing a still-healthy breast may very well help in the long run, Tuttle said. But the women in the current study did not have the BRCA gene mutations that would have greatly increased their risk of cancer in both breasts.
Tuttle and his co authors used published data to develop a model for predicting survival rates over 20 years for women diagnosed with stage I or II cancer at age 40, 50 or 60.
According to the existing data, more than 98 percent of women diagnosed with stage I breast cancer will survive at least 10 years, and 90 percent will survive for 20 years. For stage II breast cancer, 77 percent survive for at least 10 years and 58 percent survive at least 20 years.
For all age groups and tumour types in the study, the risk of developing cancer in the opposite breast after diagnosis was less than one percent each year, the authors wrote in the Journal of the National Cancer Institute.
Given how rare breast cancer in the opposite breast is for this group of women, having both breasts removed at once only increased life expectancy by at most seven months for women diagnosed with stage I cancer and less than four months for women with stage II cancer. Estimates were even lower for older women and women with oestrogen-receptor positive cancers.
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"We chose the best group that we could possibly find - women less than 40, women with oestrogen-receptor negative breast cancer, women with stage I," Tuttle told Reuters Health by phone. "Even in that group there was not a meaningful survival benefit."
Prophylactic mastectomy of the healthy breast has become much more common in recent years, in part because doctors suggest it and in part because women believe it will help them in the long run, Tuttle said.
Given that a double mastectomy essentially doubles the invasiveness and surgical risk of a one-sided mastectomy, complication rates from the surgery double as well, he said. The new model did not account for other factors including surgical complications, cost or quality of life.
In an editorial published with the study, Dr. Stephen G. Pauker and Dr. Mohamed Alseiari write, "Although the survival benefit from (removing the other breast) is small as demonstrated in this model, it is greater than zero, which suggests that for some patients even that small gain may be enough to make (the surgery) a not unreasonable choice."
Pauker and Alseiari study clinical decision-making at Tufts Medical Centre in Boston.
For those women very troubled by the 0.7 percent chance of developing cancer in the second breast, the additional surgery may be worthwhile.
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But from a societal perspective, the cost of the procedure, its complications, reconstruction and resulting negative effects on body image may outweigh the modest benefit of the extra surgery, they write.
Adding quality of life to the model would likely diminish the benefit further and turn it into a net harm, they write. Ultimately, the choice should depend on the patient's unique values and expectations.
Tuttle reiterated that his hypothetical survival model only applies to women without the BRCA mutation.
"The group that benefits primarily from contralateral mastectomy is the ones with hereditary breast cancer," he said. "I always recommend that women see a genetic counsellor and get the genetic testing."
He added, "If you have the mutation, it's a very reasonable option to consider."
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