The neutrophil-lymphocyte ratio (NLR) may indicate the balance of the inflammatory and immune systems, making NLR a useful index to evaluate tumor development. However, its prognostic value in patients with gastric cancer was still unclear. A meta-analysis was performed to characterize the prognostic effect of NLR.

An extensive literary search for relevant studies was conducted on Embase, Medline and Web of Science databases. The search strategy included the following keywords "gastric cancer", "stomach cancer", "gastric carcinoma", "stomach carcinoma", "gastric neoplasm", "stomach neoplasm", "neutrophil" and "lymphocyte" . Effect measure was hazard ratio (HR) for overall survival (OS) and progression-free survival(PFS) /disease-free survival (DFS). Then pooled HRs and 95% confidence intervals (CIs) were calculated using the random or fixed effect models by the heterogeneity of included studies. The pooled HR and 95% CI >1 indicated elevated NLR was associated with a significantly poorer OS.

This meta-analysis has been based on 18 publications and comprises a total of 5 065 patients with gastric cancer. The pooled HR showed that elevated NLR was associated with a significantly poorer OS (HR 1.79, 95%CI 1.54-2.08). Subgroup analysis showed the prognostic effect of NLR was identical in multiple treatment methods subgroup and chemotherapy subgroup[HR 1.84, (95% CI 1.48-2.29) and 1.69, (95% CI 1.41-2.03), respectively]. The same effect was also seen in NLR≤3.2 subgroup and NLR>3.2 subgroup [HR 1.80, (95% CI 1.46-2.23) and 1.93, (95% CI 1.58-2.36), respectively]. At univariate meta-regression analysis in OS, the results indicated publication year, ethnicity, NLR cutoff value, treatment type, sample size, proportion of patients in advanced stage and proportion of male did not contribute to the cause of heterogeneity(P value of 0.585, 0.887, 0.731, 0.697, 0.613, 0.877, 0.775).

The overall findings of this study support the hypothesis that elevated NLR is associated with a significantly poorer OS and NLR could be a prognostic marker in gastric cancer.