A French nationwide cohort of patients with obesity who underwent bariatric surgery were not found to be at higher risk for colorectal cancer (CRC) than the general population, according to the results of a study published in JAMA Surgery. In contrast, patients with obesity who did not undergo bariatric surgery were found to have a 34% higher risk of CRC than the general population.

Bailly and colleagues conducted the retrospective, population-based, multicenter, cohort study using French electronic health records for individuals with obesity aged 50 to 75 years and free of CRC at baseline (N=1,045,348) who were hospitalized between 2009 and 2018. Patients comparable in terms of age, sex, body mass index, follow-up status, comorbidities, and other digestive conditions were grouped according to whether they did or did not undergo bariatric surgery.

Bariatric surgery procedures included adjustable gastric banding, sleeve gastrectomy, or gastric bypass. The primary study outcome was incident CRC, and the secondary outcome was incident benign colorectal polyps.


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A majority of patients in the cohort (n = 971,217 [92.9%]) did not undergo bariatric surgery (mean age ± standard deviation [SD], 63.4 ± 7.0 years; 21.4% men/77.3% women; mean follow-up 5.3 [SD ± 2.1] years). A total of 74,131 (7.1%) patients underwent bariatric surgery (mean age ± SD, 57.3 ± 5.5 years; 22.7% men/77.3% women; mean follow-up 5.7 [SD ± 2.2] years).

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Overall, the rate of incident CRC was 1.2% (13,052 cases), and 63,649 benign colorectal polyps were diagnosed. The rate of incident CRC was 0.6% among those who underwent bariatric surgery and 1.3% among those who did not undergo bariatric surgery.

The standardized incidence ratio was 1.34 (observed/expected cases, 12,629/9417; 95% CI, 1.32-1.36) in the cohort without bariatric surgery and 1.0 (observed/expected cases, 423/428; 95% CI, 0.90-1.09) in the bariatric surgery cohort.

The propensity score-matched hazard ratio for groups with or without bariatric surgery was 0.68 (95% CI, 0.60-0.77) for incident CRC and 0.56 (95% CI, 0.53-0.59) for benign colorectal polyp.

Diagnosis of incident CRC was more frequent after adjustable gastric banding (0.7%, 115/16,460) than after gastric bypass (0.5%, 123/22,343) and sleeve gastrectomy (0.5%, 185/35,328). Diagnosis of benign colorectal polyps was more frequent after adjustable gastric banding (5.0%, 775/15,647) than after gastric bypass (3.1%, 639/20,863) or sleeve gastrectomy (3.1%, 1005/32,680).

The study was limited by its retrospective design based on historical and observational data. Patients who did not undergo bariatric surgery may not have done so due to poorer health, which would lead to selection bias in this study. Patients who underwent bariatric surgery were also younger than those who did not undergo the surgery.

“To conclude, the results of this nationwide, long-term observational study of individuals with obesity aged 50 to 75 years suggested that [bariatric surgery] is associated with decreased risk of CRC compared with no operation, exposing the individuals who undergo BS to the same CRC risk as that for the general population,” wrote the authors.

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Reference

Bailly L, Fabre R, Pradier C, Iannelli A. Colorectal cancer risk following bariatric surgery in a nationwide study of French individuals with obesity [published online March 11, 2020]. JAMA Surg. doi:10.1001/jamasurg.2020.0089