Study data published in Gastroenterology indicate that bariatric surgery substantially reduces cancer risk in adults with nonalcoholic fatty liver disease (NAFLD) and severe obesity. In a retrospective cohort study of adults with NAFLD and obesity, bariatric surgery was associated with significantly reduced odds of any cancer, including obesity-related cancer.
While NAFLD is a known risk factor for obesity and cancer, the impact of weight loss surgery on NAFLD outcomes remains unknown. To better assess the relationship between bariatric surgery and NAFLD, investigators conducted a retrospective cohort study using insurance claims data from the International Business Machines (IBM) MarketScan Database for the years 2007-2017.
The study enrolled patients 18-64 years of age with clinical diagnoses of NAFLD and severe obesity. Severe obesity was defined as having either a body mass index (BMI) ≥40 kg/m2 or a BMI ≥35 kg/m2 with significant obesity-related comorbidities.
The primary exposure was receipt of bariatric surgery, identified from inpatient and outpatient records. The primary outcome was an incident diagnosis of any cancer. Patients were followed from 12 months prior to NAFLD diagnosis until time of cancer diagnosis, end of insurance enrollment, or conclusion of study. Crude rate ratios (RRs) of each cancer type were estimated by dividing the cancer incidence rate for surgery recipients by that of non-recipients. Cox proportional hazard regression models were used to estimate the risk for cancer in patients with and without bariatric surgery.
The study cohort consisted of 98,090 patients with NAFLD and severe obesity, among whom 33,435 (34.1%) underwent bariatric surgery. Patients who underwent bariatric surgery had a younger mean age (44.01 years vs 45.93 years), were more often women (73.77% vs 62.28%), and less often had a history of smoking (6.45% vs 10.13%) compared with patients who did not undergo bariatric surgery (all P <.001).
Mean follow-up time was longer in the surgery group (31.07 months ± 24.92 months) compared with the non-surgery group (17.95 months ± 17.29 months). Overall, the surgery group experienced 1898 incident diagnoses of cancer over 115,890.11 person-years. The non-surgery group experienced 925 incident diagnoses over 67,389.82 person-years.
The crude RR for any cancer was 0.84 (95% confidence interval [CI], 0.77-0.91) among patients with surgery compared against patients without surgery. The crude RR for obesity-related cancer was 0.68 (95% CI, 0.59-0.78) in the surgery vs non-surgery group.
The adjusted risk for any cancer was reduced by 18% in the surgery group compared with controls (hazard ratio [HR], 0.82; 95% CI, 0.75-0.89). The risk for obesity-related cancer was reduced by 35% (HR, 0.65; 95% CI, 0.56-0.75). In adjusted cause-specific regression models, the surgery group had substantially lower risk than the non-surgery group for hepatocellular carcinoma (HR, 0.48; 95% CI, 0.24-0.89), pancreatic cancer (HR, 0.46; 95% CI, 0.21-0.93), endometrial cancer (HR, 0.49; 95% CI, 0.31-0.73), thyroid cancer (HR, 0.61; 95% CI, 0.41-0.89), and multiple myeloma (HR, 0.33; 95% CI, 0.14-0.69).
In post-hoc analyses, bariatric surgery was also protective against colorectal cancer (HR, 0.62; 95% CI, 0.40-0.93). Surgery-associated reductions in overall cancer risk was more pronounced in those with cirrhosis (HR, 0.52; 95% CI, 0.34-0.77) compared against those without cirrhosis (HR, 0.83; 95% CI, 0.76-0.90).
In a large, retrospective cohort of patients with NAFLD and obesity, bariatric surgery was associated with substantially reduced risk for several types of cancer. Study limitations include the use of the MarketScan database, which restricts the cohort to patients with private insurance. Additionally, the relatively short median follow-up time may have led to an underestimation in post-surgery cancer incidence.
“[O]ur study demonstrates that the risk of any cancer and obesity-related cancer is reduced in patients with NAFLD and severe obesity who undergo bariatric surgery,” investigators wrote. “Though bariatric surgery is a more aggressive approach than lifestyle modifications, surgery may provide additional benefits, such as improved quality of life and decreased long-term healthcare costs.”
Rustgi VK, Li Y, Gupta K, et al. Bariatric surgery reduces cancer risk in adults with nonalcoholic fatty liver disease and severe obesity. Gastroenterol. Published online March 17, 2021. doi: 10.1053/j.gastro.2021.03.021