Immunotherapy Improves Survival Prognosis and Reduces the Risk of Brain Metastasis in Limited-stage Small Cell Lung Cancer Patients Receiving Prophylactic Cranial Irradiation

Objective To evaluate the clinical value of immunotherapy in patients with limited-stage small-cell lung cancer (LS-SCLC) receiving prophylactic cranial irradiation (PCI), and to analyze risk factors influencing brain metastasis (BM) and survival.Methods Clinical data of 103 LS-SCLC patients who received PCI at The Affiliated Hospital of Xuzhou Medical University and Xuzhou Cancer Hospital between February 2016 and July 2024 were retrospectively analyzed. Patients were divided into an immunotherapy group (n=42) and a non-immunotherapy group (n=61) based on whether immunotherapy was administered. Kaplan-Meier method was used to calculate survival and brain metastasis rates, and the COX model was employed for prognostic factor analysis.Results The median overall survival (mOS) for the entire cohort was 32.0 months (95% CI: 26.8-37.2 months). The 1-year and 3-year BM rates after PCI were 11.3% and 28.3%, respectively. Survival analysis revealed that the immunotherapy group had significantly prolonged OS (mOS: 38.0 months vs 27.0 months, p=0.019) and a significantly lower 3-year BM rate (10.8% vs 31.7%, p=0.035). Subgroup analysis based on the timing of immunotherapy relative to PCI showed that only patients receiving immunotherapy before PCI demonstrated more significant OS benefit (mOS: 40.0 months vs 27.0 months, p=0.007) and a lower BM risk (3-year BM rate: 7.7% vs 31.7%, p=0.047) compared to the non-immunotherapy group. For patients who started immunotherapy after PCI, there were no statistically significant differences in OS or BM risk compared to the non-immunotherapy group. Multivariate analysis identified immunotherapy (HR=0.48, p=0.008), smoking history (HR=0.46, p=0.004), and extracranial metastasis (HR=1.92, p=0.012) as independent factors affecting OS. Immunotherapy (HR=0.25, p=0.019) and smoking history (HR=0.20, p=0.008) were independent factors influencing BM risk.Conclusion For LS-SCLC patients receiving PCI, early combination with immunotherapy, particularly before PCI, can effectively reduce the incidence of brain metastasis and significantly prolong survival. Furthermore, smoking history is a significant adverse risk factor affecting patient prognosis and should be emphasized in clinical management.