Nivolumab Plus 5-Fluorouracil/Leucovorin+Oxaliplatin for Gastric Cancer With Severe Peritoneal Metastasis

Based on the CheckMate 649 study, nivolumab plus chemotherapy is the first-line treatment for human epidermal growth factor receptor 2-negative advanced gastric cancer (AGC). 5-fluorouracil/leucovorin+oxaliplatin (FOLFOX) is often used for patients with AGC with severe peritoneal metastasis (PM) who cannot tolerate oral intake. Nivolumab monotherapy has shown efficacy against PM. However, the efficacy and safety of nivolumab plus FOLFOX (NIVO+FOLFOX) remain unclear. We retrospectively examined 15 patients with AGC with severe peritoneal metastasis who received NIVO+FOLFOX between January 2022 and December 2023 at our institution. Severe PM was defined as massive ascites and/or inadequate oral intake. Patients had a median age of 68 years, with 73.3% being male. Eastern Cooperative Oncology Group Performance Status 2 was observed in 20% of patients. Massive ascites was present in 86.7%, and 26.7% had inadequate oral intake. Combined positive score ≥5 was observed in 60%, and no patient had microsatellite instability-high. Median progression-free survival was 4.2 months [95% confidence interval (CI)=0.62-10.6], and median overall survival was 4.5 months (95%CI=1.48-22.5). Despite poor overall prognosis, 20.0% achieved disease control beyond 1 year. Of 13 patients with massive ascites, 38.5% responded, and 30.7% achieved complete ascites resolution. Grade ≥3 immune-related adverse events included sialadenitis, myocarditis, and hepatitis (n=1 each). No treatment-related deaths occurred. NIVO+FOLFOX was feasible for patients with AGC with severe PM, providing potential for long-term survival and ascites reduction.