BackgroundThe aim of this study is to investigate the real-world efficacy and safety of nivolumab in combination with chemotherapy for patients with advanced human epidermal growth factor receptor 2 (HER2)-negative gastric cancer (GC).MethodsWe enrolled patients diagnosed with unresectable advanced or metastatic GC who received nivolumab plus chemotherapy as first-line systemic treatment. The combined positive score (CPS), indicating the number of programmed cell death-ligand 1 (PD-L1)-stained cells, was utilized. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan–Meier method. Adverse events (AEs) were graded, and treatment was ceased upon disease progression or intolerance.ResultsA total of 27 patients were included in the study, comprising 15 patients with CPS ≥ 5 and 12 patients with CPS < 5. The objective response rate (ORR) was 55.6%, with a disease control rate (DCR) of 74.1%. Patients in the CPS ≥ 5 group exhibited higher ORR and DCR compared to those in the CPS < 5 group. Median PFS and OS were 6.1 months and 14.6 months, respectively; patients with CPS ≥ 5 showed a trend towards better PFS and OS than those with CPS < 5. Most AEs were grade 1–2, with a few instances of grade 3–4 toxicities reported, including neutropenia, thrombocytopenia, diarrhea, and anemia. There were no grade 5 AEs reported in our cohort. Furthermore, 64.7% of patients received subsequent anticancer treatment following disease progression on nivolumab plus chemotherapy.ConclusionsThe results of our study demonstrate the efficacy and safety of nivolumab plus chemotherapy in real-world practice support its adoption as a new standard first-line treatment for patients with advanced HER2-negative GC, particularly those with CPS ≥ 5.