This study plans to enroll limited-stage small cell lung cancer (LS-SCLC) patients who have achieved disease control after concurrent chemoradiotherapy (cCRT). Tissue samples collected at initial diagnosis and serial peripheral blood samples obtained at multiple post-cCRT timepoints will be analyzed using targeted next-generation sequencing to investigate the correlation between molecular residual disease (MRD) status and tumor recurrence/metastasis. For patients with MRD-positive results, a therapeutic strategy combining immunotherapy with anti-angiogenic agents will be implemented with the aim of improving clinical outcomes.