May 13, 2019

Bariatric surgery associated with reduced breast cancer risk

Kaiser Permanente study is among the first to track both premenopausal and postmenopausal women.

Bariatric surgery is associated with a nearly 40% reduction in risk of breast cancer, according to a new study from Kaiser Permanente published last month in the Annals of Surgery. This study is among the first to demonstrate an association between bariatric surgery and a reduced risk of breast cancer in both premenopausal and postmenopausal women.

“We know obesity is associated with increased risk of breast cancer. But it’s been difficult to show the impact that weight loss — such as results achieved from bariatric surgery — has on reducing breast cancer risk,” said Heather Spencer Feigelson, Ph.D., senior investigator for the Kaiser Permanente Colorado Institute for Health Research. 

Heather Spencer Feigelson, Ph.D
Heather Spencer Feigelson, Ph.D

“As obesity continues to rise in the U.S., our hope is this new study can serve as evidence to help patients see there is a clear association between sustained weight loss and reduced risk of breast cancer.”   

The study assembled nine years of data and included nearly 72,000 severely obese women (body mass index at or above 35) from four states where Kaiser Permanente members live, including Washington, Oregon, California and Colorado.

Investigators matched more than 17,000 women aged 18-79 years with a history of bariatric surgery to nearly 54,000 women with no bariatric surgery. During the observational study period, the bariatric surgery group developed 133 cases of breast cancer while the nonsurgical group developed 567 cases of breast cancer. 

For postmenopausal women with estrogen-receptor positive breast cancer, risk was reduced by 50%. For premenopausal women with estrogen-receptor negative breast cancer, risk was reduced by more than 60%.

“Breast cancer is the most common cancer in women and, currently, there are few effective strategies for reducing breast cancer risk, especially among younger women,” explained Feigelson. “While further research is needed, our study suggests women with a BMI of 35 or more can greatly reduce their risk of breast cancer through sustained weight loss.” 

Breast cancer is an active area of study for Kaiser Permanente. Scientists across the organization have used our rich, comprehensive, longitudinal data to advance knowledge in the areas of understanding risk, improving patient outcomes, and translating findings into policy and practice.