Daijiworld Media Network - Copenhagen

Copenhagen, Feb 23: A large population-based study from Nordic countries has found that gastric bypass surgery for obesity may be linked to a higher long-term risk of a rare form of stomach cancer developing in the excluded portion of the stomach, with risk appearing to rise more than a decade after surgery.

The study, conducted across Denmark, Finland and Sweden, analysed data from 109,097 bariatric surgeries, including 82,394 gastric bypass procedures and 26,703 other bariatric operations. Participants were followed for up to 44 years.

Overall, gastric non-cardia adenocarcinoma was rare, occurring in just 46 patients across the entire cohort. However, risk patterns varied over time. Compared with other bariatric procedures, gastric bypass was associated with a significantly higher risk of gastric non-cardia adenocarcinoma during the 10–44 years after surgery. In this later period, the adjusted hazard ratio was 4.0 (95% CI: 1.2–13.7). No increased risk was observed during the first 1–9 years following surgery (HR: 1.0; 95% CI: 0.3–4.2).

When compared with the general population matched by age, sex, calendar year and country, gastric bypass recipients also showed a higher incidence of this cancer in the 10–44-year period, with a standardised incidence ratio of 2.5 (95% CI: 1.4–5.0). Incidence during the first nine years was similar to expected background rates (SIR: 0.9; 95% CI: 0.4–1.4).

Among patients who developed non-cardia adenocarcinoma, outcomes appeared less favourable after gastric bypass. Gastrectomy was less commonly performed (OR: 0.3; 95% CI: 0.1–1.1), and all-cause mortality was higher (HR: 1.9; 95% CI: 0.9–3.8), although confidence intervals were wide.

Researchers noted that tumours in the excluded stomach may be harder to detect because the bypassed anatomy is difficult to access through routine endoscopy, potentially leading to delayed diagnosis.

While the absolute risk remains low, the findings highlight the need for long-term vigilance and follow-up among gastric bypass patients, particularly beyond 10 years after surgery.