Gastric cancer recent epidemiological trends in a low-risk Western population: a National Cancer Registry cohort study

Gastric cancer (GC) incidence and mortality have declined globally in age-standardised terms, but crude case numbers remain substantial in ageing Western populations. Intestinal-type (ITGC) and diffuse-type gastric cancer (DTGC), including signet-ring cell carcinoma (SRCGC), differ markedly in biology, prognosis, and therapeutic options. To date, no Irish population-based study has reported recent GC trends stratified by histological subtype. This retrospective, observational study included all incident GCs diagnosed in Ireland between 2007 and 2021, identified from the National Cancer Registry Ireland (NCRI). Variables analysed included year of diagnosis, age, sex, histology, and stage (available 2014–2019). Comparative analyses used χ² testing, and multinomial regression was applied to model adenocarcinoma not otherwise specified (NOS) cases. Crude incidence rates were calculated using Central Statistics Office population denominators. A total of 6,708 GCs were diagnosed (mean 447 cases/year). Crude incidence rates averaged 9.6 per 100,000 population. Histological breakdown showed 18% ITGC, 5% DTGC, 15% SRCGC, and 57% NOS. Regression modelling indicated that ~ 50% of NOS resembled ITGC, 38% SRCGC, and 12% DTGC. DTGC/SRCGC disproportionately affected younger and male patients and presented more often at stage IV (38–42%) than ITGC (27%). Extrapolated to NCRI projections for 2045 (1,294 cases annually), this equates to ~ 175 stage IV ITGC cases potentially eligible for oligometastatic interventions, and ~ 300–350 stage IV DTGC/SRCGC cases requiring peritoneal-directed therapies. Crude case numbers, histological subtype, and stage at presentation will determine Ireland’s future GC healthcare burden. Accurate subtyping and staging will be essential for planning advanced multimodal services.