Small cell lung cancer(SCLC) has a poor prognosis and a relatively short overall survival time, urgently requiring innovative treatment strategies to improve the prognosis of such patients. Immunotherapy has become an important component of first-line therapy for extensive-stage small cell lung cancer (ES-SCLC). Studies have found that, compared to chemotherapy alone, the combination of Surlidumab with carboplatin and etoposide can extend the median overall survival in ES-SCLC to over 15 months. However, to date, research on the use of immunotherapy in combination with concurrent chemoradiotherapy (CCRT) in limited-stage small cell lung cancer (LS-SCLC) remains limited. This study aims to explore the clinical benefits of Surlidumab in combination with concurrent chemoradiotherapy in LS-SCLC and evaluate the safety of immunotherapy in combination with CCRT as first-line treatment for LS-SCLC. At the same time, it seeks to identify tumor-related biomarkers that can effectively predict the efficacy of immunotherapy and prognosis.