This is an open-label, single-arm, single-cohort, prospective clinical study evaluating neoadjuvant antibody-drug conjugate therapy combined with immunotherapy and sequential radiotherapy followed by radical surgery in patients with high-risk upper tract urothelial carcinoma (UTUC). Eligible patients will receive neoadjuvant disitamab vedotin (RC48) plus toripalimab, followed by response-guided neoadjuvant radiotherapy and radical nephroureterectomy with bladder cuff excision. The study will assess the safety, feasibility, and preliminary antitumor activity of this multimodal neoadjuvant strategy, with pathological complete response rate as the primary endpoint.