Stage-Dependent Prognostic Impact of Younger Age in Gastric Cancer: A Nationwide Cohort Study

Although early-onset gastric cancer (EOGC; diagnosis at age <50 years) exhibits more aggressive clinicopathologic features than typical-onset gastric cancer (TOGC; diagnosis at ≥50 years), its prognostic implications remain unclear.

Data from 44,262 patients newly diagnosed with gastric cancer between 2012 and 2019 were obtained from the Korean Cancer Public Library Database. Patients were classified as having EOGC or TOGC based on age at diagnosis. All-cause and gastric cancer-specific mortality were evaluated across Surveillance, Epidemiology, and End Results (SEER) summary stages (localized, regional, and distant) using adjusted multivariable Cox proportional hazards models. The interaction between age group and cancer stage was also examined.

EOGC comprised 13.9% of cases. Compared with patients with TOGC, patients with EOGC had fewer comorbidities and were more likely to present with distant-stage disease. Nonetheless, younger patients more frequently received aggressive treatment, whereas treatment rates declined with increasing age. In localized disease, EOGC was associated with significantly lower adjusted mortality (all-cause mortality: adjusted hazard ratio [aHR], 0.52; 95% confidence interval [CI], 0.42-0.66; gastric cancer-specific mortality: aHR, 0.52; 95% CI, 0.37-0.71). In contrast, in regional and distant stages, EOGC was associated with significantly higher mortality (all-cause mortality: aHR, 2.39; 95% CI, 2.20-2.60; gastric cancer-specific mortality: aHR, 1.86; 95% CI, 1.70-2.03). Age and SEER stage showed a significant interaction (P for interaction <0.0001).

The prognostic effect of younger age in gastric cancer is stage-dependent, conferring a survival advantage in localized disease but poorer outcomes in regional and distant stages.