Prognosis and distant metastasis patterns of early-onset gastric cancer compared to late-onset: A large-scale, cross-population retrospective study

Background Early-onset gastric cancer (EOGC, ≤ 45 years) exhibits distinct clinicopathological characteristics, and its incidence is rising. This study aims to offer insights into treatment strategies for gastric cancer patients across different age groups by retrospectively analyzing the clinicopathological features, distant metastasis patterns, and prognostic factors of EOGC patients. Methods We performed a retrospective analysis of data from 33,675 gastric cancer patients in the Surveillance, Epidemiology, and End Results database and Zhejiang Cancer Hospital, including 3,208 EOGC patients and 30,467 late-onset gastric cancer (LOGC) patients. Restricted cubic spline analysis was applied to evaluate the nonlinear relationship between age and mortality risk. Propensity score matching (PSM) was employed to balance baseline differences between groups. Survival analysis was conducted using Kaplan-Meier curves, subgroup analysis, and Cox regression analysis. Result Despite EOGC patients presenting with unfavorable clinicopathological features, survival analysis revealed that EOGC patients had better overall survival than LOGC patients both before and after PSM. Subgroup analysis further indicated that EOGC patients exhibited a significant survival advantage with smaller tumor size, SRCC subtype, and stages I-III. Additionally, the distant metastasis pattern in EOGC patients differed from LOGC patients, with EOGC patients more frequently developing bone and ovarian metastases, while liver metastasis was less common. EOGC patients with peritoneal metastasis had poorer outcomes than LOGC patients. Prognosis was relatively better for EOGC patients with distant lymph node metastasis, but poorer for those with peritoneal metastasis. Conclusion Surgically treated EOGC patients have significantly better prognoses than LOGC patients. Furthermore, the distant metastasis patterns of EOGC differ from LOGC, carrying distinct prognostic implications for different metastatic sites.