The clinical significance of hyperthermic intraperitoneal chemotherapy combined with PD-1 inhibitor and systemic chemotherapy for advanced gastric cancer patients with peritoneal metastasis: a single-center retrospective study

Background Peritoneal metastasis (PM) in gastric cancer (GC) correlates with a poor prognosis. PD-1 inhibitor has significantly transformed the treatment landscape for GC, but data on the combination of HIPEC with PD-1 inhibitor and systemic chemotherapy are limited. This study evaluated the efficacy and safety of this triplet therapy as first-line treatment for GC with PM. Methods This was a retrospective, single-center study that included 34 advanced GC patients with PM. All patients received HIPEC combined with PD-1 inhibitor and systemic chemotherapy as first-line treatment (Nov 2021-Jun 2024). Primary endpoints were progression-free survival (PFS) and the duration of ascites control. Secondary endpoints were overall survival (OS) and adverse events (AEs). Results Median PFS was 7.8 months (range: 0.8-20.8), median OS was 14.3 months (range: 1.7-23.9). Patients diagnosed with moderate amount of ascites had significantly poorer PFS than with none or small amount of ascites (HR = 2.804, p = 0.0197). Univariable Cox regression analysis showed that age ≤ 60 years was associated with ascites progression (HR = 4.266, p = 0.02) and death (HR = 2.732, p = 0.04). Additionally, univariable Cox regression analysis showed that age ≤ 60 years (HR = 5.762, p = 0.001) and moderate amount of ascites (HR = 2.923, p = 0.027) were potential risk factors for disease progression. The most common adverse events were anemia, hypokalemia, thrombocytopenia and leukopenia. All adverse events were manageable. Conclusion HIPEC combined with PD-1 inhibitor and systemic chemotherapy demonstrated encouraging survival and ascites control with an acceptable safety profile in GC patients with PM.