Bariatric Surgery and the Risk of Cancer in a Large Multisite Cohort

TLDR

Obesity is strongly linked to many cancers, yet few studies have examined whether bariatric surgery reduces cancer risk. The study aimed to determine whether bariatric surgery lowers the risk of incident cancer. A retrospective cohort of 22,198 bariatric surgery patients and 66,427 matched nonsurgical controls from five sites was followed through 2014, and multivariable Cox models assessed cancer incidence up to 10 years. Bariatric surgery was associated with a 33 % lower hazard of any cancer (HR 0.67) and a 41 % lower hazard of obesity‑associated cancers (HR 0.59), with significant reductions in breast, colon, endometrial, and pancreatic cancers. Further research is needed to clarify the mechanisms by which bariatric surgery reduces cancer risk.

Abstract

To determine whether bariatric surgery is associated with a lower risk of cancer.Obesity is strongly associated with many types of cancer. Few studies have examined the relationship between bariatric surgery and cancer risk.We conducted a retrospective cohort study of patients undergoing bariatric surgery between 2005 and 2012 with follow-up through 2014 using data from a large integrated health insurance and care delivery systems with 5 study sites. The study included 22,198 subjects who had bariatric surgery and 66,427 nonsurgical subjects matched on sex, age, study site, body mass index, and Elixhauser comorbidity index. Multivariable Cox proportional-hazards models were used to examine incident cancer up to 10 years after bariatric surgery compared to the matched nonsurgical patients.After a mean follow-up of 3.5 years, we identified 2543 incident cancers. Patients undergoing bariatric surgery had a 33% lower hazard of developing any cancer during follow-up [hazard ratio (HR) 0.67, 95% confidence interval (CI) 0.60, 0.74, P < 0.001) compared with matched patients with severe obesity who did not undergo bariatric surgery, and results were even stronger when the outcome was restricted to obesity-associated cancers (HR 0.59, 95% CI 0.51, 0.69, P < 0.001). Among the obesity-associated cancers, the risk of postmenopausal breast cancer (HR 0.58, 95% CI 0.44, 0.77, P < 0.001), colon cancer (HR 0.59, 95% CI 0.36, 0.97, P = 0.04), endometrial cancer (HR 0.50, 95% CI 0.37, 0.67, P < 0.001), and pancreatic cancer (HR 0.46, 95% CI 0.22, 0.97, P = 0.04) was each statistically significantly lower among those who had undergone bariatric surgery compared with matched nonsurgical patients.In this large, multisite cohort of patients with severe obesity, bariatric surgery was associated with a lower risk of incident cancer, particularly obesity-associated cancers, such as postmenopausal breast cancer, endometrial cancer, and colon cancer. More research is needed to clarify the specific mechanisms through which bariatric surgery lowers cancer risk.