Risk Stratification in Primary Gastric Malignancies in Children, Adolescents, and Young Adults: A SEER-Based Analysis

Backgrounds: Gastric malignancies are exceptionally rare among children and young adults, and their clinicopathological characteristics and outcomes remain poorly defined. This study aimed to evaluate the demographic, clinical, and survival features of gastric cancer in patients aged ≤24 years using population-based data. Methods: Data were extracted from the Surveillance, Epidemiology, and End Results (SEER) database (2004–2016) for individuals ≤ 24 years with primary gastric malignancies. Cox proportional hazards models were used to identify predictors of overall survival (OS). Results: A total of 324 patients were included (mean age: 20 years; 50% female). Adenocarcinoma was the most common histologic subtype (52%), nearly half of which were signet ring cell carcinomas (46%). The majority of patients (59%) were diagnosed at stage IV. Median OS was 18 months, and 5-year OS was 49%. Children and adolescents (≤18 years) had significantly better survival than young adults (median OS: 34 vs. 15 months, p < 0.01). In multivariable analysis, advanced AJCC stage and higher lymph node ratio were independently associated with worse overall survival, while lymphoma histology and radiotherapy were linked to more favourable outcomes. Conclusions: Gastric cancers in patients ≤ 24 years often present at advanced stages and are dominated by aggressive histology. Prognosis is primarily determined by tumour stage, histological subtype, and lymph nodal burden. These population-based risk estimates support risk stratification and prognostic assessment in young patients by highlighting histology- and nodal-burden-driven prognostic strata.