CAIX PET/ CT Guided Radiation Therapy in CcRCC.

This is a prospective, single-arm study in adults with recurrent or metastatic clear cell renal cell carcinoma (ccRCC). Participants will receive standard systemic therapy (targeted therapy plus anti-PD-1 immunotherapy) and undergo dual PET/CT imaging (FDG PET/CT and a CAIX-targeted PET/CT) to map disease sites. When feasible, PET/CT-visible lesions will be treated with image-guided stereotactic ablative radiotherapy (SABR). Patients will be followed to evaluate progression-free survival, local control of treated lesions, and treatment-related adverse events (planned enrollment: \~70).