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

Introduction: 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%).

Conclusion: 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.