Risk of Gastric Cancer among Patients with Newly Diagnosed Ulcerative Colitis: A Nationwide Population-Based Study

Background: Few studies have investigated the risk of gastric cancer (GC) in ulcerative colitis (UC), and the results have been inconsistent. This study aimed to assess the risk of gastric cancer in newly diagnosed UC patients. Methods: Based on claims data from Korean National Health Insurance from January 2006 to December 2015, we identified 30,546 patients with UC and randomly selected 88,829 non-UC individuals as controls, who were matched by age and sex. Multivariate Cox proportional hazards regression was used to calculate adjusted hazard ratios (HRs) for gastric cancer events, with covariates taken into account. Results: During the study period, a total of 77 (0.25%) patients with UC and 383 (0.43%) non-UC individuals were diagnosed with GC. After multivariable adjustment, the HR for GC was 0.60 (95% CI: 0.47–0.77) in patients with UC, using non-UC individuals as the reference group. When stratified by age, the adjusted HRs for GC in UC patients were 0.19 (95% CI: 0.04–0.98) for those aged 20–39 years at the time of UC diagnosis, 0.65 (95% CI: 0.45–0.94) for 40–59, and 0.60 (95% CI: 0.49–0.80) for ≥60 as compared to non-UC individuals in the corresponding age groups. When stratified by sex, the adjusted HR for GC was 0.54 (95% CI: 0.41–0.73) in male UC patients of all ages. Within UC patients, a multivariable analysis revealed that the HR for GC was 12.34 (95% CI: 2.23–68.16) for those aged ≥ 60 years at the time of diagnosis of UC. Conclusions: Patients with UC had a decreased GC risk compared with non-UC individuals in South Korea. Within the UC population, advancing age (≥60 years) was identified as a significant risk factor for GC.