BackgroundThere is increasing evidence that inflammation-based biomarkers are associated with tumor microenvironment which plays important roles in cancer progression. A high lymphocyte-to-monocyte ratio (LMR), has been suggested to indicate favorable prognoses in various epithelial cancers. We performed a meta-analysis to quantify the prognostic value of LMR in advanced-stage epithelial cancers undergoing various treatment.MethodsWe searched PubMed, EMBASE, Web of science and Cochrane Library up to July 2018 for relevant studies. We included studies assessing the prognostic impact of pretreatment LMR on clinical outcomes in patients with advanced-stage epithelial cancers. The primary outcome was overall survival (OS) and the secondary outcome was progression free survival (PFS). The summary hazard ratio (HR) and 95% confidence interval (CI) were calculated.ResultsA total of 8984 patients from 35 studies were included. A high pretreatment LMR was associated with favorable OS (HR=0.578, 95% CI 0.522-0.641, P<0.001) and PFS (HR=0.598, 95% CI 0.465-0.768, P<0.001). The effect of LMR on OS was observed among various tumor types. A higher pretreatment LMR was associated with improved OS in chemotherapy (n=10, HR=0.592, 95% CI 0.518-0.676, P<0.001), surgery (n=10, HR=0.683, 95% CI 0.579-0.807, P<0.001) and combined therapy (n=11, HR=0.507, 95% CI 0.442-0.582, P<0.001) in the subgroup analysis by different therapeutic strategies. The cut-off value for LMR was 3.0 (range=2.35-5.46). Subgroup analysis according to the cut-off value showed a significant prognostic value of LMR on OS and PFS in both subgroups.ConclusionsA high pretreatment LMR is associated with favorable clinical outcomes in advanced-stage epithelial cancers undergoing different therapeutic strategies. LMR could be used to improve clinical decision-making regarding treatment in advanced epithelial cancers.