Cancer in the Excluded Stomach After Gastric Bypass Surgery for Obesity

To assess whether gastric bypass surgery for obesity increases the risk of adenocarcinoma in the excluded stomach and delays adenocarcinoma diagnosis.

Gastric bypass might increase adenocarcinoma risk through bile reflux and delay such diagnosis because of anatomical hurdles with endoscopic access.

This population-based cohort study included patients having undergone bariatric surgery in Denmark, Finland, or Sweden. Cancer risk after gastric bypass was compared with (1) other bariatric procedures using Cox regression, providing hazard ratios (HR) with 95% confidence intervals (CI), adjusted for confounders, and (2) the general population of similar age, sex, calendar year, and country by calculating standardized incidence ratios (SIR). Gastrectomy rates and all-cause mortality were compared between bariatric procedures using logistic regression, providing odds ratios (OR), and Cox regression providing HRs, respectively.

During up to 44 years of follow-up of 109,097 bariatric surgeries (82,394 gastric bypasses; 26,703 other bariatric surgeries), 46 (0.04%; 30 after gastric bypass; 16 after other bariatric surgeries) patients developed gastric non-cardia adenocarcinoma. Compared to other bariatric surgeries and the general population, gastric bypass was associated with an increased risk of gastric non-cardia adenocarcinoma between 10-44 years after surgery (HR=4.0, 95%-CI 1.2-13.7; SIR=2.5, 95%-CI 1.4-5.0), but not within the first 1-9 years (HR=1.0, 95%-CI 0.3-4.2; SIR=0.9, 95%-CI 0.4-1.4). Among the non-cardia adenocarcinoma patients, the gastrectomy rate was seemingly decreased (OR=0.3, 95%-CI 0.1-1.1) and all-cause mortality increased (HR=1.9, 95%-CI 0.9-3.8) after gastric bypass.

Gastric bypass might increase the risk of adenocarcinoma in the excluded stomach and delay the detection when such tumors occur. Yet, this cancer is still rare after gastric bypass.