Prognostic Value of Lactate Dehydrogenase-to-Lymphocyte Ratio in Limited-Stage Small Cell Lung Cancer

Background: The lactate dehydrogenase (LDH)-to-lymphocyte ratio (LLR) is a simple, non-invasive prognostic marker. We aimed to reveal the prognostic role that LLR plays in limited-stage small cell lung cancer (LS-SCLC).Methodology: This study was a retrospective analysis of 497 patients diagnosed with LS-SCLC from 2015 to 2018, pretreated with LDH, and whose absolute lymphocyte counts were recorded. Patients were categorized into two groups based on their LLR scores: high-risk (LLR >= 182) and low-risk (LLR <182). The Kaplan-Meier test was used to plot the survival curve, and the log-rank test helped evaluate the differences in survival between the high- and low-risk groups. Variables associated with overall survival (OS) and progression-free survival (PFS) were assessed using multivariate and univariate analyses. Additionally, the inverse probability of treatment weight (IPTW) and propensity score matching (PSM) methods helped minimize the selection and confounding bias.Results: The high LLR group had 151 patients, and the low LLR group had 346 patients. In the statistical analysis, we found that the patients' PFS and OS were significantly decreased in the high LLR group (PFS: 7.85 vs. 10.41 months, p < 0.0001; OS: 13.4 vs. 18.6 months, p < 0.0001). LLR was an independent prognostic factor for OS (hazard ratio [HR]: 0.719; p = 0.004) and PFS (HR: 0.714; p = 0.002). Similar results were obtained after compensating and matching with the IPTW or PSM methods.Conclusion: Pre-treatment LLR is a potential marker against PFS and OS in patients with LS-SCLC.