Response-Guided Bladder Preservation With Trastuzumab Rezetecan, Adebrelimab, and Concurrent Bladder Radiotherapy in HER2-Expressing Muscle-Invasive Bladder Cancer

This prospective, multicenter, open-label phase II study will evaluate a response-guided bladder-preservation strategy in patients with HER2-expressing muscle-invasive bladder cancer. Participants will receive maximal transurethral resection of the bladder tumor, trastuzumab rezetecan plus adebrelimab, and concurrent bladder radiotherapy. Treatment response will be assessed by cystoscopic biopsy or diagnostic transurethral resection at 8 weeks (±2 weeks) after radiotherapy. Participants with a pathological stage of T1 or lower may continue bladder-preserving management, whereas radical cystectomy will be recommended for participants with disease above T1. The primary outcome is the major pathological response rate.