Preoperative neutrophil-to-lymphocyte ratio is a predictor of survival of epithelial ovarian cancer: a systematic review and meta-analysis of observational studies

Inflammation plays an important role in the development and progression of epithelial ovarian cancer (EOC). However, no meta-analysis has comprehensively and quantitatively investigated the prognostic value of the neutrophil-to-lymphocyte ratio (NLR) in EOC patients. Therefore, we performed a meta-analysis to quantify the prognostic impact of this biomarker. We searched the PubMed and Web of Science databases from their inception through December 31, 2016, and examined observational studies evaluating the association of preoperative NLR with progression-free survival (PFS) and overall survival (OS) of EOC patients. A random-effects model was used to summarize hazard ratios (HRs) with 95% confidence intervals (CIs). Twelve retrospective cohort studies including 3,154 EOC patients were identified. Elevated NLR in EOC patients was associated with worse PFS (summarized HR =1.80; 95% CI = 1.22-2.65; I-2 = 79.1%) and OS (summarized HR = 1.72; 95% CI = 1.18-2.51; I-2 = 73.5%) compared with low NLR. No evidence of publication bias was detected by funnel plot analysis and formal statistical tests. Although the results were robust in all subgroup analyses, not all results were statistically significant. We determined that adjustments for CA-125 level and performance status might be sources of heterogeneity. These combined results indicate that preoperative NLR is an important predictor of prognosis in EOC patients. Since the high heterogeneity and retrospective study design of included studies, these results require further validation with prospective cohort and trials enrolling larger patient populations and conducting longer follow-up examinations.