Platelet-Lymphocyte Ratio as a Predictor of Prognosis in Head and Neck Cancer: A Systematic Review and Meta-Analysis.

The aim of this systematic review and meta-analysis was to investigate the prognostic utility of the platelet-to-lymphocyte ratio (PLR) in head and neck cancer. Medline (via PubMed), EMBASE, Scopus, and the Cochrane Library databases were searched from their inception to May 2017 for relevant literature. A systematic review and meta-analysis were performed to generate the pooled hazard ratios (HR) for overall survival (OS) and disease-specific survival (DSS). The study was conducted in accordance with the Cochrane Handbook and PRISMA guidelines. Risk of bias was assessed using the QUIPS tool. The logarithm of the HR with standard error was used as the primary summary statistic. Heterogeneity was assessed using Cochran's Q and Higgins' I2. A total of 13 studies were included in the final analysis, combining data from 4,541 patients. The results demonstrated that an elevated PLR was significantly associated with poorer OS [HR 1.85, 95% CI 1.35-2.52, p < 0.00001] and DSS [HR 1.57, 95% CI 1.25-1.97, p < 0.0001]. Significant heterogeneity was detected for the pooled end points. Subgroup analysis demonstrated reduction of heterogeneity by controlling for sample size and cutoff value. 95% prediction intervals showed wide ranges crossing the null threshold.