An LDH-based prognostic model for extensive-stage small-cell lung cancer patients treated with chemo-immunotherapy and consolidative thoracic radiotherapy

Background Extensive-stage small-cell lung cancer (ES-SCLC) is a highly aggressive malignancy with poor long-term survival despite multimodal therapy. Endocrine and metabolic alterations have been increasingly recognized as contributors to tumor progression and potential prognostic indicators. Lactate dehydrogenase (LDH), a readily available biomarker reflecting tumor metabolic activity, has been associated with outcomes in various cancers. However, its prognostic significance in ES-SCLC patients receiving combined chemo-immunotherapy and consolidative thoracic radiotherapy remains unclear. Methods Between 2019 and 2025, 81 stage III-IV ES-SCLC cases treated with chemo-immunotherapy and subsequent consolidative chest radiation were retrospectively reviewed. Clinical variables and blood biomarkers were collected. To evaluate prognosis, we employed Kaplan-Meier curves and Cox proportional hazards modeling. Having identified serum LDH as an autonomous prognostic marker through multivariate analysis, we categorized it using a clinical threshold of 250 U/L for in-depth study. Subsequently, we developed a prognostic nomogram for estimating OS at 1- and 2- years. Time-dependent ROC analysis conducted at the 12- and 24-mo nth marks was utilized to evaluate the model’s discriminative power. Results In total, 81 patients were included in the final analysis. Multivariable Cox regression demonstrated that serum LDH was independently associated with poorer overall survival (hazard ratio HR 1.006 per 1 U increase, 95% confidence interval CI 1.003–1.009; p 0.001). Kaplan–Meier analysis using a clinically defined LDH threshold demonstrated significantly reduced overall survival among patients with elevated LDH levels (250 U/L) compared with those with lower LDH values (≤250 U/L; p=0.0012). The prognostic nomogram incorporating LDH, AJCC stage, the systemic immune-inflammation index (SII), and immunotherapy status demonstrated moderate discriminative ability, with an area under the curve for OS of 0.731 at 12 months and 0.694 at 24 months. Conclusions Our analysis indicates that serum LDH retains independent prognostic relevance for overall survival among ES-SCLC patients treated with combined chemo-immunotherapy and consolidative thoracic radiotherapy. The nomogram integrating LDH provided 1- and 2-year OS predictions, which may facilitate risk stratification and guide personalized management in the era of chemo-immunotherapy.