title: Prognostic role of platelet to lymphocyte ratio in solid tumors: a systematic review and meta-analysis.
abstract: BACKGROUND
  Inflammation influences cancer development and progression. An elevated platelet to lymphocyte ratio (PLR), a marker of inflammation, has been linked to poor prognosis in several malignancies. Here, we quantify the prognostic impact of this biomarker.
  
  
  METHODS
  A systematic review of databases was conducted to identify publications exploring the association of blood PLR and overall survival (OS) in solid tumors. Data were pooled in a meta-analysis. Pooled HRs for OS by disease group and by PLR cutoff groups were computed and weighted using generic inverse-variance and random-effect modeling.
  
  
  RESULTS
  Twenty studies comprising 12,754 patients were assessed. Cutoffs for PLR defining risk groups ranged from 150 to 300 and were dichotomous (12 studies; group 1) or split into three groups (<150/150-300/>300, 8 studies; group 2). Higher PLR was associated with significantly worse OS in group 1 [HR = 1.87; 95% confidence interval (CI, 1.49-2.34); P < 0.001] and with a nonsignificant association in group 2 (HR per higher category = 1.21; 95%CI, 0.97-1.50; P = 0.10). The size of effect of PLR on OS was greater for metastatic disease (HR[group 1] = 2.0; 95% CI, 1.6-2.7; HR[group 2] = 1.6; 95% CI, 1.1-2.4) than for early-stage disease (HR[group 1] = 1.5; 95% CI, 1.0-2.2; HR[group 2] = 1.0; 95% CI, 0.8-1.3). A significant association was observed for colorectal, hepatocellular, gastroesophageal, ovarian, and pancreatic carcinoma in group 1 and for colorectal cancers in group 2.
  
  
  CONCLUSIONS
  A high PLR is associated with worse OS in various solid tumors. Further research of its regulation and relevance in daily practice is warranted.
  
  
  CONCLUSIONS
  PLR is a readily available and inexpensive biomarker with independent prognostic value in solid tumors.
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Arnoud J
authors.initials: AJ
authors.lastname: Templeton
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Olga
authors.initials: O
authors.lastname: Ace
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Mairéad G
authors.initials: MG
authors.lastname: McNamara
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Mustafa
authors.initials: M
authors.lastname: Al-Mubarak
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Francisco E
authors.initials: FE
authors.lastname: Vera-Badillo
authors.affiliation: Department of Surgical Oncology, Department of Surgery, Princess Margaret Cancer Centre, University of Toronto, Toronto, Canada;
authors.forename: Thomas
authors.initials: T
authors.lastname: Hermanns
authors.affiliation: Department of Medical Oncology, Institute of Oncology Ljubljana, Slovenia; and.
authors.forename: Boštjan
authors.initials: B
authors.lastname: Seruga
authors.affiliation: Translational Oncology Unit, University Hospital, Albacete, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Ocaña
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine;
authors.forename: Ian F
authors.initials: IF
authors.lastname: Tannock
authors.affiliation: Authors' Affiliations: Division of Medical Oncology and Hematology, Department of Medicine; eitan.amir@uhn.ca.
authors.forename: Eitan
authors.initials: E
authors.lastname: Amir
mesh_terms: D006801:Humans; D018655:Lymphocyte Count; D009369:Neoplasms / Q000097:blood* / Q000401:mortality*; D010976:Platelet Count; D011379:Prognosis