The risk of developing colorectal cancer risk (CRC) increases after bariatric surgery, according to a study presented at Digestive Disease Week by researchers from Health & Science University, Portland, Oregon and The Ohio State University, Columbus, OH. Their findings were outlined in the study, ‘The impact of bariatric surgery on colorectal cancer risk: a matched analysis using a nationwide US cohort’ (Presentation Number: Sa025), after the investigators assessed CRC risk using a large US cohort and after accounting for multiple confounders.
For the study, the researchers compared adults ≥18 years old with BMI ≥40 kg/m2 who underwent roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (VSG) to non-surgical subjects with BMI ≥40 kg/m2 (controls). Using data fro the 2012-2018 MarketScan nationwide insurance claims database, they matched 321,358 controls to 86,025 BRS cases (up to 4:1 matching ratio) for age, sex, Charlson comorbidity index and follow-up length. Multivariable Cox, proportional hazards ratio (HR), was used to examine the incidence of CRC ≥1 year after bariatric surgery vs. matched controls. They restricted their analysis to a matched case-control cohort with colonoscopy and compared CRC rate after adjusting for additional confounders.
The outcomes revealed 31 (0.035%) incidents of CRC were diagnosed between one and seven years after surgery vs 71 (0.012%) in controls. Patients undergoing bariatric surgery had a trend towards a 67% higher hazard of developing CRC during follow-up vs matched non-surgical patients with BMI ≥40 kg/m2 (p=0.08). They added that this trend was consistent irrespective of age, gender or type of surgery; however, it was most pronounced in adults who had VSG <50 years of age (p=0.08).
In their sensitivity analysis, 8,947 bariatric surgery cases with colonoscopy were matched to 34,744 controls, which revealed is an increased risk of CRC on colonoscopy after both types of bariatric surgery (p=0.001).
The authors stated that their findings are consistent with data from UK and Swedish cohort studies, adding that aetiology is likely to be multifactorial (eg, surgery-induced elevation in Glucagon-like peptide-1 and colonic microbiome changes) and prospective multi-centre studies are necessary to investigate these findings and devise preventative strategies in this growing at-risk cohort.