Background: Predictive factors of nivolumab treatment response in patients with gastric cancer (GC) remain unclear.
Methods: In this retrospective cohort study, tissue specimens of patients with unresectable or recurrent GC and prior or scheduled treatment with nivolumab as third-line or higher therapy between September 2017 and February 2019 were collected from 23 institutions. The tumour-positive score (TPS) and combined positive score (CPS) of PD-L1 expression and mismatch repair (MMR) were analysed by immunohistochemistry. Associations between clinicopathological factors and tumour-response rate, hyperprogressive disease (HPD) rate and survival were assessed.
Results: Of 200 eligible patients, 143 had measurable lesions. The response and HPD rates were 17.5% and 22.1%, respectively. The response rate was significantly higher in patients with performance status (PS) 0-1 (P = 0.026), non-peritoneal metastasis (P = 0.021), PD-L1 TPS ≥ 1 (P = 0.012), CPS ≥ 5 (P = 0.007) or ≥ 10 (P < 0.001) or MMR deficiency (P < 0.001). The HPD rate was significantly higher in patients with PS 2-3 (P = 0.026), liver metastasis (P < 0.001) and CPS < 10 (P = 0.048). Multivariate analysis revealed that CPS (P = 0.001) and MMR (P = 0.002) were independent prognostic factors of progression-free survival, as well as liver metastasis (P < 0.001), peritoneal metastasis (P = 0.004) and CRP (P < 0.001).
Conclusions: PD-L1 CPS and MMR could be useful biomarkers for nivolumab treatment efficacy in GC.
Clinical trial registration: UMIN000032164.