Esophagus to Small Intestine
Association of bariatric surgery with cancer risk and mortality in adults with obesity
Importance: Obesity increases the incidence and mortality from some types of cancer, but it remains uncertain whether intentional weight loss can decrease this risk.
Objective: To investigate whether bariatric surgery is associated with lower cancer risk and mortality in patients with obesity.
Design, setting, and participants: In the SPLENDID (Surgical Procedures and Long-term Effectiveness in Neoplastic Disease Incidence and Death) matched cohort study, adult patients with a body mass index (BMI) ≥ 35 who underwent bariatric surgery at a US health system between 2004 and 2017 were included. Patients who underwent bariatric surgery were matched 1:5 to patients who did not undergo surgery for their obesity, resulting in a total of 30,318 patients. Follow-up ended in February 2021.
Exposures: Bariatric surgery (n = 5053), including Roux-en-Y gastric bypass and sleeve gastrectomy, versus non-surgical care (n = 25,265).
Main outcomes and measures: Multivariable Cox regression analysis estimated time to incident obesity-associated cancer (a composite of 13 cancer types as the primary end point) and cancer-related mortality.
Results: The study included 30,318 patients (median age, 46 years; median BMI, 45; 77% female; and 73% White) with a median follow-up of 6.1 years (interquartile range, 3.8–8.9 years). The mean between-group difference in body weight at 10 years was 24.8 kg (95% confidence interval [CI]: 24.6–25.1 kg) or a 19.2% (95% CI: 19.1–19.4%) greater weight loss in the bariatric surgery group. During follow-up, 96 patients in the bariatric surgery group and 780 patients in the non-surgical control group had an incident obesity-associated cancer (incidence rate [IR] of 3.0 events vs. 4.6 events, respectively, per 1000 person-years). The cumulative incidence of the primary end point at 10 years was 2.9% (95% CI: 2.2–3.6%) in the bariatric surgery group and 4.9% (95% CI: 4.5–5.3%) in the non-surgical control group (absolute risk difference, 2.0%, 95% CI: 1.2–2.7%; adjusted hazard ratio [aHR] = 0.68, 95% CI: 0.53–0.87; p = 0.002). Cancer-related mortality occurred in 21 patients in the bariatric surgery group and 205 patients in the non-surgical control group (IR of 0.6 events vs. 1.2 events, respectively, per 1000 person-years). The cumulative incidence of cancer-related mortality at 10 years was 0.8% (95% CI: 0.4–1.2%) in the bariatric surgery group and 1.4% (95% CI: 1.1–1.6%) in the non-surgical control group (absolute risk difference, 0.6%, 95% CI: 0.1–1.0%; aHR = 0.52, 95% CI: 0.31–0.88; p = 0.01).
Conclusions and relevance: Among adults with obesity, bariatric surgery compared with no surgery was associated with a significantly lower incidence of obesity-associated cancer and cancer-related mortality.