Clinical outcomes in advanced gastric cancer among elderly patients (≥80 years old) treated with chemotherapy.

351 Background: In aging societies, the proportion of elderly patients with advanced gastric cancer (AGC) is increasing; however, clinical evidence regarding chemotherapy (CTx) in patients aged ≥80 years remains limited. Methods: We retrospectively analyzed patients with AGC who received first-line CTx at Nagoya Medical Center between 2009 and 2024. Patients were stratified into three age groups: <70, 70–79, and ≥80 years. The primary outcome was overall survival (OS). Secondary outcomes included time to treatment failure (TTF) of first-line CTx, objective response rate (ORR), and the proportion of patients receiving subsequent-line therapy. Survival was estimated by the Kaplan–Meier method and compared using the log-rank test. Prognostic factors were evaluated by multivariable Cox regression. Results: A total of 322 patients were included (<70 years: 144; 70–79 years: 124; ≥80 years: 54). With increasing age, baseline Eastern Cooperative Oncology Group Performance Status (ECOG PS, p=0.007), hemoglobin (p=0.002), albumin (p=0.028), creatinine clearance (p<0.001), and Prognostic Nutritional Index (p=0.025) were worse. S-1 monotherapy was more frequently selected in patients aged ≥80 years (p=0.037). Median survival time was 10.7, 12.8, and 7.1 months in the <70, 70–79, and ≥80 groups, respectively (p=0.074). Median TTF was 4.6, 5.9, and 2.8 months (p=0.711). The ORR of first-line therapy was 49.0%, 56.5%, and 51.5% in the three groups, respectively (p=0.417). Treatment discontinuation due to toxicity occurred in 7.2%, 14.9%, and 24.5% of patients (p=0.005). The proportion of patients who did not receive subsequent-line therapy was 35.9%, 44.7%, and 64.2% (p=0.002). In multivariable analysis, age ≥80 was not an independent prognostic factor, whereas ECOG PS, neutrophil-to-lymphocyte ratio, oral intake, and treatment era (pre- vs post-nivolumab approval) were independently associated with OS. Conclusions: Although outcomes in patients ≥80 years were unfavorable, chronological age alone was not a definitive prognostic determinant. Appropriate patient selection, treatment modification, and supportive care are essential to optimize outcomes in this population.