Association of Bariatric Surgery With Cancer Incidence in Patients With Obesity and Diabetes: Long-term Results From the Swedish Obese Subjects Study

Abstract

<b>OBJECTIVE</b> <p>Obesity and type 2 diabetes are associated with serious, adverse health effects, including cancer. Although bariatric surgery has been shown to reduce cancer risk in patients with obesity, the effect of bariatric surgery on cancer risk in patients with obesity and diabetes is less studied. We therefore examined the long-term incidence of cancer after bariatric surgery and usual care in patients with obesity and diabetes in the matched prospective Swedish Obese Subjects (SOS) study. </p> <p><b>RESEARCH DESIGN AND METHODS</b></p> <p>The SOS study examines long-term outcomes following bariatric surgery or usual care. The current analysis includes 701 patients with obesity and type 2 diabetes at baseline, 393 of which underwent bariatric surgery, and 308 who received conventional obesity treatment. Information on cancer events was obtained from the Swedish National Cancer Register. Median follow-up time was 21.3 years (interquartile range 17.6-24.8 years, maximum 30.7 years). </p> <p><b>RESULTS</b></p> <p>During follow-up, the incidence rate for first-time cancer was 9.1 per 1000-person-years (95% CI, 7.2-11.5) in patients with obesity and diabetes treated with bariatric surgery and 14.1 per 1000-person-years (95% CI, 11.2-17.7) in patients treated with usual obesity care (HRadj=0.63; 95% CI 0.44-0.89, p=0.008). Moreover, surgery was associated with reduced cancer incidence in women (HRadj=0.58; 0.38-0.90, p=0.016), although the sex-treatment interaction was non-significant (p=0.630). In addition, diabetes remission at the 10-year follow-up was associated with reduced cancer incidence (HRadj=0.40; 95% CI 0.22-0.74, p=0.003).</p> <p><b>CONCLUSIONS</b></p> <p>These results suggest that bariatric surgery prevents cancer in patients with obesity and diabetes, and that durable diabetes remission is associated with reduced cancer risk. </p>