Multicentre biomarker cohort study on the efficacy of nivolumab treatment for gastric cancer

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.