Pilot Study on Rutin Combined With Tislelizumab and GC (Gemcitabine and Cisplatin) as Neoadjuvant Therapy for Platinum-refractory Muscle-invasive Bladder Cancer

This trial aims to evaluate the efficacy, safety, and biological mechanisms of rutin combined with tislelizumab and GC(Gemcitabine and Cisplatin) in platinum-refractory muscle-invasive bladder cancer patients. Key research questions include: 1. Whether rutin regulates epigenetic mechanisms in tumor cells from platinum-refractory bladder cancer patients and modulates the tumor immune microenvironment. 2. Evaluating the safety and adverse events of the combination treatment in platinum-refractory bladder cancer patients. 3. Assessing the disease control rate in platinum-refractory bladder cancer patients receiving this therapy. Patients with MIBC who exhibit no response (stable disease or progressive disease) after two cycles of neoadjuvant GC chemotherapy will receive two cycles of rutin combined with tislelizumab and GC. Safety and adverse events will be assessed after each cycle of combinational treatment. Therapeutic response will be evaluated by contrast-enhanced MRI, and surgical decisions (transurethral resection, partial cystectomy, or radical cystectomy) will be made by two senior urologists. Epigenetic alterations and the changes in immune microenvironment will be analyzed post-treatment.