Cadonilimab Combined With Stereotactic Radiotherapy as Second-line Treatment for Brain Metastases

The goal of this clinical trial is to evaluate the efficacy and safety of Cadonilimab combined with stereotactic radiation therapy in the second-line treatment of brain metastases from non-small cell lung cancer (NSCLC). The main questions it aims to answer are: * Does Cadonilimab combined with SRT in the second-line treatment of brain metastases provide better results? * Is the toxicity of Cadonilimab combined with SRT manageable in second-line treatment of brain metastases? Researchers will compare evaluate the efficacy and safety of Cadonilimab combined with SRT as a second-line treatment for patients with advanced NSCLC： * Receive Cadonilimab combined with SRT for brain lesions. * Visit the hospital regularly once every 12 weeks for checkups and tests