Elevated peripheral blood neutrophil-to-lymphocyte ratio is associated with an immunosuppressive tumour microenvironment and decreased benefit of PD-1 antibody in advanced gastric cancer

Background Due to its limited efficacy and potential toxicity, anti-PD-1 monoclonal antibody is not suitable for all advanced gastric cancer (AGC) patients and predictive biomarkers identifying patients who can benefit from it are urgently needed. This study aimed to evaluate the predictive and prognostic value of inflammatory markers in the context of the systemic inflammatory status and tumour microenvironment. Methods The study included 58 patients from a prospective study investigating the safety and efficacy of toripalimab in chemorefractory AGC patients. Patient characteristics, treatment outcomes, and haematological parameters were analysed. Immune-cell infiltration and gene expression in tumour tissue were examined using transcriptome sequencing. Results In this cohort, the median follow-up time was 4.5 months, the median progression-free survival was 1.9 months, and the median overall survival (OS) was 4.8 months. The objective response rate was 12.1% and th disease control rate (DCR) was 39.7%. Both the baseline blood neutrophil-to-lymphocyte ratio (bNLR) with a cut-point of 2.7 and the early elevated dynamic change of the bNLR (dNLR) with a cut-point of 1.5 were prognostic factors of survival. Patients in the high bNLR or dNLR group had remarkably poor DCR (25.8% vs 59.1%, P = 0.023; 15.8% vs 54.6%, P = 0.008). In multivariate analysis, bNLR and tumour mutational burden were independent prognostic factors of OS. Tumour RNA-seq analysis revealed enriched neutrophil infiltration and a higher tumour NLR in the bNLR-high group. Corresponding tumour gene-expression profiles were associated with neutrophil recruitment and inflammatory cytokine aggregation. Conclusions Our study demonstrated the potential clinical utility of NLR as a biomarker for patient selection and clinical management in predicting the prognosis of AGC patients as well as response to anti-PD-1 therapy. In addition, high bNLR reflected the imbalance of tumour-tissue-infiltrating neutrophils and lymphocytes, and was associated with an immunosuppressive and pro-tumour microenvironment.