NORDIC data link gastric bypass to rare, excluded stomach cancer, with risk rising after 10 years and diagnosis potentially delayed.
Long-Term Signals After Gastric Bypass
In a population-based cohort study spanning Denmark, Finland, and Sweden, investigators assessed whether gastric bypass surgery for obesity is associated with adenocarcinoma arising in the excluded stomach and whether diagnosis may be delayed due to challenges accessing the bypassed anatomy endoscopically. The cohort included 109,097 bariatric surgeries, of which 82,394 were gastric bypasses and 26,703 were other bariatric surgeries, with follow-up extending up to 44 years.
Across the full cohort, gastric non-cardia adenocarcinoma remained uncommon, occurring in 46 patients overall. However, patterns differed over time. When comparing gastric bypass with other bariatric procedures, the risk of gastric non-cardia adenocarcinoma was higher in the later period, specifically 10–44 years after surgery. In that window, gastric bypass was associated with an adjusted hazard ratio of 4.0 (95% CI: 1.2–13.7). In contrast, no increased risk signal was observed within the first 1–9 years after surgery (HR: 1.0; 95% CI: 0.3–4.2).
Cancer in the Excluded Stomach After Gastric Bypass
To contextualize risk against background rates, the authors also compared gastric bypass recipients with the general population matched by age, sex, calendar year, and country. The standardized incidence ratio suggested higher incidence in the 10–44-year period (SIR: 2.5; 95% CI: 1.4–5.0), while incidence in years 1–9 was similar to expected (SIR: 0.9; 95% CI: 0.4–1.4).
Among patients who developed non-cardia adenocarcinoma, outcomes also appeared less favorable after gastric bypass. Gastrectomy was seemingly less common (OR: 0.3; 95% CI: 0.1–1.1), and all-cause mortality was higher (HR: 1.9; 95% CI: 0.9–3.8), though confidence intervals were wide.
Overall, the findings suggest that gastric bypass might increase long-term risk of rare, excluded stomach cancer and may delay detection when tumors occur, underscoring the importance of long-horizon vigilance while keeping the absolute risk in perspective.
Reference: Leijonmarck W et al. Cancer in the Excluded Stomach After Gastric Bypass Surgery for Obesity. Annals of Surgery. 2026;doi:10.1097/SLA.0000000000007035.
