title: A systematic review and meta-analysis on the impact of pre-operative neutrophil lymphocyte ratio on long term outcomes after curative intent resection of solid tumours.
abstract: BACKGROUND
  There is increasing evidence to suggest that cancer-associated inflammation is associated with poorer long-term outcomes. Various markers have been studied over the past decade in an attempt to improve selection of patients for surgery. This meta-analysis explored the association between the neutrophil-lymphocyte ratio and prognosis following curative-intent surgery for solid tumours.
  
  
  METHODS
  Studies were identified from US National Library of Medicine (Medline) and the Exerpta Medica database (EBASE) performed in March 2013. A systematic review and meta-analysis were performed to generate combined hazard ratios for overall survival (OS) and disease-free survival (DFS).
  
  
  RESULTS
  Forty-nine studies containing 14282 patients were included. Elevated NLR was associated with poorer overall survival [HR: 1.92, 95% CI (1.64-2.24)] (p < 0.001) and disease-free survival [HR: 1.99, 95% CI (1.80-2.20)] (p < 0.001). Significant heterogeneity was found with an I(2) of 77% and 97% for OS and DFS respectively. Subgroup analyses demonstrated that gastro-intestinal malignancies; mainly gastric [HR: 1.97, 95% CI (1.41-2.76)], colorectal [HR: 1.65, 95% CI (1.21-2.26)] and oesophageal [HR: 1.48, 95% CI (0.91-2.42)] cancers were predictive of OS (I(2) = 54.3%). A separate analysis for studies using an NLR cutoff of 5 demonstrated significantly poorer outcomes [HR: 2.18, 95% CI (1.74-2.73)] (p = 0.002) with less heterogeneity (I(2) = 58%).
  
  
  CONCLUSIONS
  Elevated NLR correlates with poorer prognosis. It potentially represents a simple, robust and reliable measure that may be useful in identifying high-risk groups who could benefit from adjuvant therapy.
authors.affiliation: Department of Surgery, Western Health, Footscray, Victoria, Australia.
authors.forename: Ashvin
authors.initials: A
authors.lastname: Paramanathan
authors.affiliation: UNSW Department of Surgery, St. George Hospital, Kogarah, Sydney, New South Wales 2217, Australia.
authors.forename: Akshat
authors.initials: A
authors.lastname: Saxena
authors.affiliation: UNSW Department of Surgery, St. George Hospital, Kogarah, Sydney, New South Wales 2217, Australia. Electronic address: david.morris@unsw.edu.au.
authors.forename: David Lawson
authors.initials: DL
authors.lastname: Morris
mesh_terms: D006801:Humans; D008214:Lymphocytes / Q000473:pathology*; D009369:Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000601:surgery; D009504:Neutrophils / Q000473:pathology*; D011300:Preoperative Care; D011379:Prognosis; D015996:Survival Rate
keywords: Meta-analysis; Neutrophil lymphocyte ratio; Prognosis; Resection; Surgery; Systematic review