A new study shows that the increasingly popular practice of “preventive mastectomy” in non-cancerous breasts provides no benefit to the vast majority of women.
“It’s important for women to understand that, except for one subset of breast cancer patients, they don’t need to do this,” said lead author Isabelle Bedrosian of University of Texas M.D. Anderson Cancer Center. “Hopefully, it’ll reassure patients wondering if they should.”
Approximately 40,000 women die from breast cancer in the United States each year, and another 200,000 cases are diagnosed. Because cancer in one breast is known to increase the risk of cancer recurrence in the other breast, doctors are increasingly recommending that cancer survivors opt to have both breasts removed as a “preventive” measure. And women are opting for it in huge numbers, seeking the peace of mind that it is said to offer.
The number of preventive mastectomies in the United States increased two-and-a-half-fold between 1998 and 2003. Today, 11 percent of all women undergoing a mastectomy on a cancerous breast choose to have the non-cancerous breast removed as well. Analysts have attributed this increase to more advanced screening techniques that detect cancers smaller and earlier; popularization of genetic screening and the idea that some genes may predispose families to breast cancer; and wider public acceptance of plastic surgery combined with advances in reconstructive technology.
Yet while it has been strongly established that elective mastectomy does reduce the risk of breast-cancer recurrence, there has been no research to suggest that it actually lengthens a woman’s life span.
“We have not had real data to guide us,” Bedrosian said. “We can’t sit down with a woman and say, ‘If you do this, this is your expected benefit.’ And when we don’t have those data, then biases become the big drivers of decision making.”
In the new study, published in the Journal of the National Cancer Institute, Bedrosian and colleagues analyzed the records of 107,106 women in the National Cancer Institute’s Surveillance, Epidemiology and End Results registry. All the women had undergone a mastectomy to treat breast cancer of Stage III or lower; 8,902 had chosen to have a healthy breast removed, as well.
After controlling for other risk factors, the researchers found only a small difference in survival rates between women who had chosen to have two breasts removed and women who had chosen to have only one removed. Upon further analysis, they discovered that this benefit was only present in women under the age of 50 with estrogen receptor-negative, early-stage tumors. In this group, elective mastectomy increased the survival rate by 4.8 percent, amounting to just under five lives saved for every 100 surgeries.
Elective mastectomy provided no survival benefit to women outside this demographic.
The researchers believe that even when cancers recur, most women will not be killed by them but will instead die of other causes first. Only in women whose cancers lack estrogen receptors and who would otherwise have long lives ahead of them does recurrence appear to pose a serious threat to survival.
The most effective breast cancer drugs on the market are those that lower the body’s production of estrogen, which fuels the growth of many cancers. Tumors that lack estrogen receptors do not depend on the hormone for their growth, however, meaning that women with these cancers cannot use the most effective drugs and tend to have higher mortality rates.
Breast-cancer specialist Larry Norton of Memorial Sloan-Kettering Cancer Center in New York City expressed skepticism about the study’s methodology and cautioned against doctors and patients giving it too much weight.
“This is an observational study, and hence it is impossible to control for confounding variables,” Norton said, “and should not be used for individual clinical decisionmaking.”
Norton admitted, however, that ethics make it impossible to perform a true controlled study on the question, since such an experiment might end up increasing cancer mortality in one group of participants.
Bedrosian disputed Norton’s criticism, noting that the researchers used rigorous statistical analysis and controlled well for interference from other variables. She believes that the conclusions are, in fact, strong enough to help women make better-informed decisions about elective mastectomy.
“We looked at this in multiple different ways, and we got the same answer every time. And the results make good clinical sense. That adds another level of reassurance,” she said. “Our hope is that when women hear the numbers, they will take a second look and decide not to go forward with a preventive mastectomy [in their healthy breast] if it won’t give them a survival benefit.”
Victor Vogel, national vice president for research at the American Cancer Society, said the results suggest that women should wait a full year before going through with the removal of a healthy breast.
“In a younger woman with [estrogen receptor]-negative disease, an [elective} mastectomy may be considered,” he said. “In the vast majority of women older than 50 with ER-positive disease, prudent waiting is probably the most appropriate.”
Bedrosian said that the point of the study was not to impose “a uniform mandate” that women should never get the procedure, but that their decisions must be well informed.
“This is still a decision to be made by the patient after talking with her doctor,” Bedrosian said.
“We hope this study helps women make better decisions [and] provides some reassurance that perhaps a [preventive] mastectomy is not necessary, perhaps overly aggressive and perhaps a bit too much.”