Colorectal Cancer Risk Following Bariatric Surgery in a Nationwide Study of French Individuals With Obesity

IMPORTANCE: Although bariatric surgery is effective against morbid obesity, the association of this surgery with the risk of colorectal cancer remains controversial. OBJECTIVE: To assess whether bariatric surgery is associated with altered risk of colorectal cancer among individuals with obesity. DESIGN, SETTING, AND PARTICIPANTS: This retrospective, population-based, multicenter, cohort study based on French electronic health data included 1 045 348 individuals with obesity, aged 50 to 75 years, and free of colorectal cancer at baseline. All inpatients with obesity having data recorded during a hospital stay between 2009 and 2018 by the French national health insurance information system database were followed up for a mean (SD) of 5.3 (2.1) years for those who did not undergo bariatric surgery and 5.7 (2.2) years for those who underwent bariatric surgery. Two groups of patients comparable in terms of age, sex, body mass index, follow-up, comorbidities, and conditions who did or did not undergo surgery were also obtained by propensity score matching. EXPOSURES: Bariatric surgery (n = 74 131), including adjustable gastric banding, sleeve gastrectomy, gastric bypass; or no bariatric surgery (n = 971 217). MAIN OUTCOMES AND MEASURES: Primary outcome was incident colorectal cancer. Standardized incidence ratios were calculated using age-, sex-, and calendar year–matched colorectal cancer incidence among the general French population during the corresponding years. Secondary outcome was incident colorectal benign polyps. RESULTS: Among a total of 1 045 348 patients, the mean (SD) age was 57.3 (5.5) years for the 74 131 patients in the surgical cohort vs 63.4 (7.0) years for the 971 217 patients in the nonsurgical cohort. The mean (SD) follow-up was 6.2 (2.1) years for patients who underwent adjustable gastric banding, 5.5 (2.1) years for patients who underwent sleeve gastrectomy, and 5.7 (2.2) years for patients who underwent gastric bypass. In total, 13 052 incident colorectal cancers (1.2%) and 63 649 colorectal benign polyps were diagnosed. The rate of colorectal cancer was 0.6% in the bariatric surgery cohort and 1.3% in the cohort without bariatric surgery. In the latter cohort, 9417 cases were expected vs 12 629 observed, a standardized incidence ratio of 1.34 (95% CI, 1.32-1.36). In the bariatric surgery cohort, 428 cases were expected and 423 observed, a standardized incidence ratio of 1.0 (95% CI, 0.90-1.09). Propensity score–matched hazard ratios in