Lymphocyte-to-monocyte ratio is an independent prognostic factor in surgically treated small cell lung cancer: An international multicenter analysis

Introduction: The prognostic value of lymphocyte-to-monocyte ratio (LMR) has already been evaluated in a wide range of malignancies including patients with non-surgically managed small cell lung cancer (SCLC). However, the impact of LMR on survival in surgically treated SCLC patients has not yet been assessed. The aim of this study was to determine the clinical role of LMR in patients undergoing surgical resection for SCLC. Materials and methods: In this retrospective study, individuals receiving radical surgery for SCLC between January 2000 and December 2019 from three participating European institutions were included. LMR was calculated from the most recent blood test prior to surgery. Optimal cut-off values for LMR were determined and correlated with clinical data and survival outcomes. Results: In total, 101 patients underwent surgical resection for SCLC during the study period. 76 (75.2%) received anatomic lung resection (defined as lobectomy or pneumonectomy), 63 (62.4%) were male and the median age was 63 (range 41-80) years. LMR > 2.50 significantly associated with improved overall survival (OS) (35.3 vs. 20.7 months, p = 0.032) and disease-free survival (DFS) (25.8 vs 18.5 months, p = 0.011). Moreover, multivariate Cox proportional hazard model identified LMR > 2.50 as an independent prognostic factor of longer OS (hazard ratio (HR) 0.617; 95% confidence interval (CI) 0.383-0.993; p = 0.047) and DFS (HR 0.505; 95% CI 0.266-0.959; p = 0.037). Conclusion: Preoperatively elevated LMR is a robust prognostic factor associated with improved OS and DFS in patients undergoing surgery for SCLC. Further studies are warranted to better understand the overall impact of LMR when applying surgery in these patients.