Bariatric surgery is independently associated with a decrease in the development of colorectal lesions.

Background: Obesity is a risk factor for colorectal cancer and possibly the formation of precancerous, colorectal polyps . Bariatric surgery is very effective for long-term weight loss; however, it is not known whether bariatric surgery decreases the risk of subsequent colonic neoplasia. We hypothesized that bariatric surgery would decrease the risk of developing colorectal lesions (new cancer and precancerous polyps).

Methods: We reviewed all patients (n = 3,676) who underwent bariatric surgery (gastric bypass, sleeve gastrectomy, or gastric banding) at the University of Virginia (Charlottesville, VA) 1985-2015. Obese, nonoperative patients (n = 46,873) from an institutional data repository were included as controls. Cases and controls were propensity score matched 1:1 by demographics, comorbidities, body mass index, and socioeconomic factors. The matched cohort was compared by univariate analysis and conditional logistic regression.

Results: A total of 4,462 patients (2,231 per group) with a median follow-up of 7.8 years were well-matched with no statistically significant baseline differences in initial body mass index (48 vs 49 kg/m), sex, and age in addition to other comorbidities (all P > .05). The operative cohort had more weight loss (55.5% vs -1.4% decrease in excess body mass index, P < .0001). The operative cohort developed fewer colorectal lesions (2.4% vs 4.8%, P < .0001). We observed no differences in polyp characteristics or staging for patients who developed cancer (all P > .05). After risk adjustment, bariatric surgery was independently associated with a decrease in new colorectal lesions (OR 0.62, 95% CI 0.42-0.91, P = .016).

Conclusion: Bariatric surgery was associated with lesser, risk-adjusted incidence of new colorectal lesions in this large population of propensity matched patients undergoing bariatric surgery compared with a control group not undergoing bariatric surgery. These results suggest the benefits of bariatric surgery may extend beyond weight loss and mitigation of comorbidities.