Supplementary Material for: Multicenter Study on the Safety and Efficacy of First-Line Nivolumab-Combination Chemotherapy in Patients Aged 75 years and Older with Unresectable Advanced or Recurrent Gastric Cancer

Introduction: Nivolumab combined with chemotherapy has been approved as the first-line treatment for HER2-negative, unresectable, advanced, or recurrent gastric cancer. Patients aged ≥ 75 years more often have impaired organ function and comorbidities that increase the risk of adverse events, including immune-related adverse events, than younger patients, potentially limiting the continuation of treatment. In this multicenter study, we aimed to evaluate the safety and efficacy of first-line nivolumab chemotherapy in older patients. Methods: We retrospectively analyzed data from 103 patients treated with first-line nivolumab combination chemotherapy for unresectable, advanced, or recurrent gastric cancer at 12 institutions between November 2021 and January 2023. The participants were divided into groups A (<75 years, n=67) and B (≥75 years, n=36). Results: The mean age was 63.9 years in Group A and 78.6 years in Group B. Body weight was significantly lower in Group B (p=0.041), and performance status 0–1 and hypertension were more prevalent in Group B (both p<0.01). Chemotherapy regimens and incidence of grade ≥3 immune-related adverse events were similar between the groups. The median overall survival was 15.2 months in Group A and was not reached in group B; this difference was not significant (p=0.689). Conclusions: First-line chemotherapy with nivolumab is safe and effective in patients aged ≥75 years with a good performance status, as in younger patients, suggesting that it is a valid treatment option for the former subgroup.