Weight Loss Surgery May Lower Risk of Breast Cancer, Research Suggests

Weight loss surgery may reduce the risk of developing breast cancer in obese individuals, even among those with a genetic predisposition towards cancer, new research suggests.

The research was presented at the American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting at ObesityWeek 2019, in a session titled “Does Bariatric Surgery prevent cancer in the obese population? A nationwide case-control analysis.”

Although it’s not totally clear why the link exists, obesity is associated with an increased risk of developing several types of cancer, including breast cancer. Weight loss surgery, also called bariatric surgery, is one of the most effective procedures for weight loss; as such, it follows that this surgery may reduce breast cancer risk.

To test this idea, researchers analyzed data from the National Inpatient Sample. This included data for 1,670,035 obese women, 246,668 of whom underwent bariatric surgery and 1,423,367 of whom did not.

For the analysis, obesity was defined as a body mass index (BMI) of 35 kg/m². BMI — a ratio of a person’s weight and height — doesn’t convey much information about body fat, but in large datasets like this, a very high BMI can generally indicate obesity for the majority of the population.

The researchers found that breast cancer rates were significantly lower (79% lower) among those who underwent bariatric surgery, compared with those who did not.

Interestingly, among individuals with a genetic predisposition for breast cancer, the cancer rates were more than two times higher in the group that did not get the surgery (18.0% vs. 7.4%). The criteria used for determining genetic predisposition in this study were not specified in the presentation abstract.

“Our findings suggest bariatric surgery could significantly prevent the development of cancer in patients with a higher risk than the average population, even in those genetically predisposed,” co-investigator Emanuele Lo Menzo, MD, PhD, of Cleveland Clinic Florida, said in a press release. “The effect we saw on patients genetically predisposed to developing breast cancer was remarkable and we believe this is the first time a study has shown such an impact.”

“Further studies are needed to determine the factors, including weight loss, that may have led to such risk reduction,” he added.

The study’s results should be considered preliminary as they have not undergone peer review. Additionally, the data only show an association, not a cause-and-effect relationship. While the simplest explanation for the reduced cancer rate is that the surgery led to weight loss, which in turn lowered the likelihood that tumors would grow, the data don’t demonstrate this definitively.

“We are not suggesting that everyone who is obese have surgery,” co-investigator Raul Rosenthal, MD, also of Cleveland Clinic Florida, stated in another press release. “We strongly suggest that the U.S. population needs to be aware that obesity is linked to the potential of developing all sorts of cancer.”

Eric J. DeMaria, MD, the president of the ASMBS, who was not involved in the research, said that “cancer prevention is a new frontier in research about bariatric surgery and the data is compelling. The evidence continues to mount that patients and doctors considering bariatric surgery should look beyond weight loss in terms of its benefits.”