Novel insights into autoimmune gastritis: clinical profile and gastric neoplastic risk from an international multicentre study

Background International comparative data on autoimmune gastritis (AIG) remain limited. Objective We aimed to describe AIG features and quantify the risk of gastric adenocarcinoma and type 1 gastric neuroendocrine tumours (NETs). Design Retrospective study across eight tertiary centres in Europe, Türkiye, Latin America, the USA and Japan. Adults with histologically confirmed AIG were included. Clinical and follow-up data were collected to estimate adenocarcinoma and NET incidence and associated factors. Results 1240 patients were included (female:male 2:1; median age 59, IQR 48–67; median follow-up 68 months, IQR 36–108). Macrocytic anaemia predominated in Europe (45.6%), microcytic anaemia in Türkiye (56.1%) and Latin America (64.7%). Autoimmune comorbidities were most frequent in Latin America (67.7%). 36 (2.9%) gastric adenocarcinomas and 132 (10.6%) NETs occurred. No incident adenocarcinomas were reported in Latin America or Japan cohorts. Crude incidence rates ranged from 1.15 to 1.47 for adenocarcinoma and 0.70 to 1.62/100 person-years for NETs. Factors associated with adenocarcinoma included age >65 years (OR 4.50, 95% CI 2.18 to 9.27), intestinal metaplasia (OR 1.51, 95% CI 1.16 to 1.97), gastrin-17 >1316 pg/mL (OR 15.52, 95% CI 3.61 to 66.71) and prior proton pump inhibitor (PPI) (OR 5.74, 95% CI 2.13 to 15.47). For NETs, prior PPI (OR 2.69, 95% CI 1.12 to 6.46), smoking (OR 2.45, 95% CI 1.75 to 3.42), intestinal metaplasia (OR 2.88, 95% CI 1.38 to 6.01) and gastrin-17 >1316 pg/mL (OR 3.25, 95% CI 1.42 to 7.45), were associated with higher odds, while Helicobacter pylori eradication was associated with lower odds of NETs (OR 0.25, 95% CI 0.07 to 0.88). Conclusion AIG presentation and neoplastic risks differ by region, warranting further research and potentially region-specific follow-up strategies.