Prognostic Value of Pretreatment Lymphocyte-to-Monocyte Ratio in Lung Cancer: A Systematic Review and Meta-Analysis

BACKGROUND: The overall prognosis of lung cancer remains unfavorable and novel prognostic biomarkers of lung cancer are needed warranted. Accumulating evidence indicate that systemic inflammation plays a vital role in lung cancer. The lymphocyte-to-monocyte ratio (LMR) is biomarker that reflects the level of systemic inflammation. OBJECTIVE: To perform a comprehensive meta-analysis exploring the correlation of pretreatment LMR with the overall survival (OS) and progression-free survival (PFS) of lung cancer patients. METHODS: We conducted searches of the PubMed, Embase, Cochrane Library, and Web of Science databases to May 2020 to identify relevant studies and calculated combined hazard ratios (HRs) to evaluate the association between pretreatment LMR and survival time in patients with lung cancer. RESULTS: A total of 23 studies comprising 8361 lung cancer patients were included. Among the patients, 5702 (68%) were males, 4548 were current smokers and 2212 were diagnosed with squamous carcinoma. The pooled analysis revealed that decreased pretreatment LMR was significantly correlated with reduced of PFS (HR = 1.49, 95% CI: 1.34-1.67, p < 0.01) and reduced OS (HR = 1.61, 95% CI: 1.45-1.79, p < 0.01) among lung cancer patients. Furthermore, in the subgroup analyses according to histologic type, a lower level of pretreatment LMR seemed to be unrelated to the poorer OS of small cell lung cancer (SCLC) patients (HR = 1.21, 95%CI: 0.87-1.67, P = 0.25). CONCLUSIONS: Decreased pretreatment LMR in peripheral blood was associated with shorter OS and PFS in lung cancer patients, suggesting its potential prognostic value.