Prognostic Impact of Baseline Neutrophil-to-Lymphocyte Ratio and Its On-Treatment Change on Survival Outcomes in Advanced Small-Cell Lung Cancer: A Retrospective Analysis

Background: Reliable and readily accessible prognostic biomarkers for extensive-stage small-cell lung cancer (ES-SCLC) are still lacking. The neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has shown prognostic relevance in several malignancies; however, its dynamic changes during treatment have not been well characterized in SCLC. Methods: We retrospectively analyzed patients with ES-SCLC who received systemic chemotherapy between January 2010 and December 2024. Baseline NLR was calculated within 7 days before first-line treatment, and on-treatment NLR was assessed at 6 weeks. A predefined NLR cutoff value of 5 was applied, and changes in NLR (ΔNLR) were defined as the difference between 6-week and baseline values. Associations with time to treatment failure (TTF) and overall survival (OS) were evaluated. Results: A total of 176 patients were enrolled. High baseline NLR (≥5) was significantly associated with shorter TTF and OS (both p < 0.01). An increase in NLR during treatment (ΔNLR ≥ 0) was significantly associated with poorer OS. Combined assessment of baseline NLR and ΔNLR identified distinct prognostic groups, with patients exhibiting both high baseline NLR and ΔNLR ≥ 0 demonstrating markedly poor survival. In multivariate analyses, baseline NLR, ΔNLR, performance status, and immune checkpoint inhibitor combination therapy were independent predictors of survival. Baseline NLR analyzed as a continuous variable showed a significant inverse correlation with TTF and OS. Conclusions: Combined evaluation of baseline NLR and its on-treatment change provides improved prognostic stratification in patients with ES-SCLC.