Real-world survival benefit of chemotherapy in elderly patients with advanced gastric cancer: a population-based SEER analysis

Using the U.S. Surveillance, Epidemiology, and End Results (SEER-21) database, we examined age-specific patterns of systemic chemotherapy utilization and survival outcomes among elderly and oldest-old patients with advanced gastric cancer (GC). Patients diagnosed with stage IV GC between 2004 and 2022 were stratified into four age groups (< 65, 65–74, 75–84, and ≥ 85 years). Clinicopathological characteristics and chemotherapy use were compared across age categories. Overall survival (OS) and cancer-specific survival (CSS) were evaluated using Kaplan–Meier analyses, and the association between chemotherapy and OS was assessed using propensity score-based inverse probability weighting and weighted Cox regression models. Among 56,478 eligible patients, chemotherapy utilization declined markedly with advancing age, from 69% in patients younger than 65 years to 20% in those aged 85 years or older. Chemotherapy was associated with significantly improved OS and CSS across all age groups (log-rank P < 0.0001). After adjustment, chemotherapy remained independently associated with improved OS in every age category, including patients aged 85 years or older (hazard ratio 0.40, 95% confidence interval 0.37–0.44). These findings demonstrate that systemic chemotherapy provides meaningful survival benefits even in the oldest-old population and underscore the importance of individualized, geriatric-informed treatment decision-making in advanced GC.