By establishing a prospective clinical cohort for small cell lung cancer (SCLC) and systematically collecting high-quality real-world data integrating clinical, imaging, pathological, and molecular dimensions, this study aims to enable personalized treatment for distinct SCLC subtypes. Furthermore, by evaluating the influence of radiotherapy timing, dose and fractionation, and target selection on efficacy and toxicity, we aim to identify the optimal radio-immunotherapy combination regimen that maximizes the synergistic effect in SCLC patients.