Prognostic significance of immune cells in non-small cell lung cancer: meta-analysis

BACKGROUND: Tumor-associated immune cells are prognostic in non-small cell lung cancer (NSCLC) but findings have been conflicting. OBJECTIVES: To determine the prognostic role of immune cells according to localization in NSCLC patients. METHODS: A systematic literature review and meta-analysis was performed on dendritic cell (DC), tumor associated macrophages (TAM), mast cells (MC), natural killer (NK) cells, T and B cells and tumor CTLA-4 and PD-L1 studies. RESULTS: We analysed 96 articles (n= 21,752 patients). Improved outcomes were seen with increased tumor DCs (overall survival (OS) hazard ratio (HR) 0.55; 95% confidence interval (CI) 0.44–0.68), NK cells (OS HR 0.45; 0.31–0.65), TAMs (OS HR 0.33; 0.17–0.62), M1 TAMs (OS HR 0.10; 0.05–0.21), CD3+ T cells (disease specific survival (DSS) HR 0.64; 0.48–0.86), CD8+ T cells (OS HR 0.78; 0.66–0.93), B cells (OS HR 0.65; 0.42–0.99) and with increased stroma DC (DSS HR 0.62; 0.47–0.83), NK cells (DSS HR 0.51; 0.32–0.82), M1 TAMs (OS HR 0.63; 0.42–0.94), CD4+ T cells (OS HR 0.45; 0.21–0.94), CD8+ T cells (OS HR 0.77; 0.69–0.86) and B cells (OS HR 0.74;0.56–0.99). Poor outcomes were seen with stromal M2 TAMs (OS HR 1.44; 1.06–1.96) and Tregs (relapse free survival (RFS) HR 1.80; 1.34–2.43). Tumor PD-L1 was associated with worse OS (1.40; 1.20–1.69), RFS (1.67) and DFS (1.24). CONCLUSION: Tumor and stroma DC, NK cells, M1 TAMs, CD8+ T cells and B cells were associated with improved prognosis and tumor PD-L1, stromal M2 TAMs and Treg cells had poorer prognosis. Higher quality studies are required for confirmation.