Bariatric Surgery Reduces Cancer Risk in Adults With Nonalcoholic Fatty Liver Disease and Severe Obesity

Background & Aims: Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and increased risk of cancer. The impacts of bariatric surgery on cancer risk in NAFLD patients are unknown. We investigated the effect of bariatric surgery on cancer risk in patients with NAFLD and severe obesity using the MarketScan database. Methods: We conducted a retrospective cohort study of 18 to 64 years old newly diagnosed NAFLD patients with severe obesity between 2007 and 2017. We used Cox proportional hazard models to examine the association between bariatric surgery, modeled as a time-varying covariate, and the risks of any cancer and obesity-related cancer, while accounting for confounding using inverse probability of treatment weighting (IPTW). Results: A total of 98,090 patients were included in the study, 33,435 (34.1%) received bariatric surgery. In those without surgery, 1898 incident cases of cancer occurred over 115,890.11 person-years of follow-up, compared with 925 cancer cases over 67,389.82 person-years among surgery patients (crude rate ratio, 0.84; 95% CI, 0.77- 0.91). The IPTW-adjusted risk of any cancer and obesity-related cancer was reduced by 18% (hazard ratio, 0.82; 95% CI, 0.76–0.89) and 25% (hazard ratio, 0.65; 95% CI, 0.56–0.75), respectively, in patients with versus without bariatric surgery. The adjusted risks of any cancer and obesity-related cancer were significantly lower in cirrhotic versus non-cirrhotic patients who underwent surgery. In cancer-specific models, bariatric surgery was associated with significant risk reductions for colorectal, pancreatic, endometrial, thyroid cancers, hepatocellular carcinoma, and multiple myeloma. Conclusion: Bariatric surgery was associated with significant reductions in the risks of any cancer and obesity-related cancer in NAFLD patients with severe obesity.