Investigators found that many women opt for a preventive mastectomy despite knowing it will be unlikely to improve their chance of survival.

Young women with breast cancer often overestimate the odds that cancer will occur in their other, healthy breast, and decide to have the healthy breast surgically removed, according to a study published in the Archives of Internal Medicine. The research team, which included investigators from Dana-Farber Cancer Institute (DFCI) and Brigham and Women’s Hospital (BWH), found that many women opt for the procedure – known as a contralateral prophylactic mastectomy, or CPM – despite knowing it will be unlikely to improve their chance of survival.

“An increasing percentage of women treated for early-stage breast cancer are choosing to have CPM,” says the study’s lead author, Dr. Shoshana Rosenberg, of Susan F. Smith Center for Women’s Cancers at Dana-Farber/Brigham and Women’s Cancer Center. “The trend is particularly notable among younger women.”

The survey results, explained Dr. Rosenberg, suggest that many patients are going into this decision with an unrealistic sense of the benefits and risks of CPM.

Researchers surveyed 123 women age 40 or younger who had undergone a bilateral mastectomy – the removal of both breasts – despite having cancer in only one breast. Respondents answered questions about their reasons for having the procedure, their knowledge of its risks and benefits, and their satisfaction with the outcome.

Almost all the women said they opted for CPM out of a desire to improve their chances of survival and prevent the cancer from spreading to other parts of the body. At the same time, however, most understood that removing both breasts does not extend survival for women who are free of an inherited genetic predisposition to breast cancer.

The survey also indicated that women who don’t inherit an increased genetic risk of breast cancer tend to overestimate the chance that cancer will develop in both breasts. They estimated that 10 out of 100 women with cancer in one breast would develop cancer in the other breast within five years. The actual risk of that happening is approximately two to four percent.

By contrast, respondents who did have an inherited predisposition to breast cancer – as a result of a mutation in the genes BRCA1 or BRCA2, for example – more accurately perceived their risk for cancer in both breasts.

“Our findings underscore how important it is that doctors effectively communicate the risks and benefits of CPM to women,” said Dr. Rosenberg. “We need to be sure that women are making informed decisions, supported decisions, based on an accurate understanding of the pros and cons of the procedure, and in a setting where anxiety and concerns can be addressed.”

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This post originally appeared on Insight, the blog of Dana-Farber Cancer Institute.

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