Prognostic role of pretreatment blood neutrophil-to-lymphocyte ratio in advanced cancer survivors: A systematic review and meta-analysis of 66 cohort studies

Background Neutrophil-to-lymphocyte ratio (NLR) is crucial for the incidence and mortality of various tumors. However, little is known on NLR and its association with prognosis in advanced tumors. Here we performed a meta-analysis to establish the prognostic significance of pretreatment blood NLR for advanced tumors. Methods A systematic literature search through April 2016 was performed to evaluate the association between pretreatment blood NLR and overall survival (OS) or progression-free survival (PFS) in patients with advanced tumors. Data were extracted from studies reporting hazard ratios (HRs) and 95% confidence interval (CI) and pooled using the Mantel–Haenszel random-effect model. Results Sixty-six studies with a total of 24536 individuals were included in the meta-analysis. Pooled analyses revealed that elevated pretreatment NLR was associated with worse OS (HR 1.70, 95% CI 1.57–1.84, P < 0.001) and PFS (HR 1.61, 95% CI 1.42–1.82, P < 0.001) in advanced tumors. Subgroup analysis stratified by tumor type demonstrated that pancreatic cancer patients with high pretreatment NLR had the worst OS (HR 1.94, 95% CI 1.55–2.54, P < 0.001) and colorectal cancer with the worst PFS (HR 1.74, 95% CI 1.04–2.90, P < 0.001). When stratified by cut-off value for NLR, we found that cut-off value being five indicated the worst PFS (HR 2.23, 95% CI 1.54–3.23, P = 0.019). Conclusions Overall, high pretreatment blood NLR could be an adverse prognostic indicator for advanced tumor. Large-scale prospective studies investigating its survival outcomes in specific cancer type are strongly advocated.