A Retrospective Cohort Study on Pretreated Neutrophil-to-Lymphocyte Ratio and Prognosis of Small Cell Lung Cancer: Evidence of Effect Modification by Chemotherapy Regimen

PURPOSE: Neutrophil-to-lymphocyte ratio (NLR) has been suggested as an independent risk factor for progression-free survival (PFS) and overall survival (OS) in small cell lung cancer (SCLC). However, it is still unknown whether there is a linear relationship between the NLR and the risk of death in SCLC. The objective of this study is to provide further results. PATIENTS AND METHODS: A retrospective cohort study was performed among a total of 251 participants with SCLC. Smooth curve fitting and piecewise Cox regression model were used to determine the linear relationship between NLR and mortality risk. A multivariable Cox regression model was used to estimate the effects of NLR on OS. Interaction and stratified analyses were conducted according to covariates. RESULTS: The analysis indicated no significant nonlinear relationship or threshold effect between NLR and hazard of death. Multivariate analysis revealed that every unit increase in NLR was associated with a 10% increase in mortality risk. High NLR (>3.5) at baseline was associated with poor OS (hazard ratio [HR]=1.97, P=0.009). The difference in median OS duration between the high and low NLR groups was statistically significant (9.1 months vs 14.6 months, P=0.0067). Furthermore, interaction analysis identified the chemotherapy regimen to play an interactive role in the association between NLR and hazard of death. CONCLUSION: NLR was identified as an independent risk factor for OS in SCLC and the linear correlation was observed between them. Administration of etoposide plus cisplatin (EP) regimen in patients with low NLR resulted in better long-term outcome than that of etoposide plus carboplatin (EC) regimen, while administration of the EC regimen conferred longer OS than that of the EP regimen in patients with high NLR.