Survival Benefit of Adjuvant S-1 Chemotherapy in Patients Aged ≥ 80 Years with Gastric Cancer after Curative Resection: A Multicenter Cohort Study.

Abstract

The efficacy of adjuvant chemotherapy for gastric cancer (GC) in adult patients aged ≥ 80 years remains unclear because this population is often underrepresented in clinical trials. This study aimed to evaluate the impact of S-1 adjuvant chemotherapy on this age group following curative gastrectomy. This retrospective multicenter study included 113 patients aged ≥ 80 years with pathological stage II/III GC who underwent curative D2 or D1+ gastrectomy between 2008 and 2020. Patients were classified according to whether they had received S-1 adjuvant chemotherapy. Overall survival (OS), recurrence-free survival (RFS), adverse events, and relative dose intensity (RDI) were analyzed. Among the patients, 30 received S-1 and 83 underwent surgery alone. Baseline characteristics were generally balanced, although the S-1 group had a higher rate of D2 dissection and shorter postoperative hospital stays. The 5-year OS and RFS rates were significantly higher in the S-1 group (70.0% and 66.7%, respectively) than in the nonchemotherapy group (48.1% and 45.7%, respectively). Multivariable analysis confirmed S-1 administration as an independent prognostic factor for both OS and RFS. Grade ≥ 3 adverse events occurred in 22.3% of patients who received S-1. Patients who maintained an RDI ≥ 60% demonstrated improved RFS. Adjuvant chemotherapy with S-1 may improve survival in patients aged ≥ 80 years with stage II/III GC. Maintaining an adequate dose intensity appears to be critical for clinical benefits in this population.