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

Educational Objective To identify the risk of colorectal cancer in patients with obesity following bariatric surgery.
1 Credit CME
Key Points

Question  What is the risk of colorectal cancer following bariatric surgery?

Findings  In a nationwide cohort study in France (2009-2018), the risk of colorectal cancer was estimated using standardized incidence ratios for 1 045 348 inpatients with obesity aged 50 to 75 years. The standardized incidence ratio was 1.0 following bariatric surgery vs 1.34 for individuals with obesity who did not undergo bariatric surgery.

Meaning  Following bariatric surgery, individuals with obesity appear to share the same risk of colorectal cancer as that of the general population.


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 comparable operated vs nonoperated groups were 0.68 (95% CI, 0.60-0.77) for colorectal cancer and 0.56 (95% CI, 0.53-0.59) for colorectal benign polyp. There were fewer new diagnoses of colorectal cancer after gastric bypass (123 of 22 343 [0.5%]) and sleeve gastrectomy (185 of 35 328 [0.5%]) than after adjustable gastric banding (115 of 16 460 [0.7%]), and more colorectal benign polyps after adjustable gastric banding (775 of 15 647 [5.0%]) than after gastric bypass (639 of 20 863 [3.1%]) or sleeve gastrectomy (1005 of 32 680 [3.1%]).

Conclusion and Relevance  The results of this nationwide cohort study suggested that following bariatric surgery, patients with obesity share the same risk of colorectal cancer as the general population, whereas for patients with obesity who do not undergo bariatric surgery, the risk is 34% above that of the general population.

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Article Information

Accepted for Publication: December 26, 2019.

Corresponding Author: Laurent Bailly, MD, PhD, Département de Santé Publique, Centre Hospitalier Universitaire de Nice, Hôpital Archet 1, Niveau1 151 Route Saint Antoine de Ginestière CS 23079 06202, Nice Cedex 3, France (

Published Online: March 11, 2020. doi:10.1001/jamasurg.2020.0089

Author Contributions: Dr Bailly had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Bailly, Pradier, Iannelli.

Acquisition, analysis, or interpretation of data: Bailly, Fabre, Pradier.

Drafting of the manuscript: Bailly, Iannelli.

Critical revision of the manuscript for important intellectual content: Fabre, Pradier, Iannelli.

Statistical analysis: Bailly, Fabre, Pradier.

Administrative, technical, or material support: Pradier.

Supervision: Pradier, Iannelli.

Conflict of Interest Disclosures: None reported.

Additional Contributions: Brigitte Dunais, MD, formerly employed by the Nice University Public Health Department, made substantial contributions to the writing and editing of this article. The Agence Technique de l’Informatique Hospitalière provided equipment used for data collection. No one received any compensation for the stated contribution.

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