Biomarker-Enriched Kidney-Preserving Strategy With Disitamab Vedotin Plus Tislelizumab in HER2-Positive High-Risk Upper Tract Urothelial Carcinoma

Inclusion Criteria: * Age ≥18 years at the time of informed consent. * Histologically confirmed upper tract urothelial carcinoma (UTUC) arising from the renal pelvis or ureter, based on ureteroscopic biopsy. * High-risk UTUC, defined by at least one of the following features: Tumour size ≥2 cm; High-grade cytology or biopsy; Radiographic evidence of local invasion (≥cT2); Hydronephrosis; Multifocal disease * Clinical stage cT1-T3, N0-N1, M0, based on radiographic assessment. * N1 disease is permitted only if lymph nodes are considered resectable. * HER2-positive disease, defined as immunohistochemistry (IHC) score of 1+，2+ or 3+ on tumour tissue, assessed according to predefined criteria. * At least one measurable lesion according to RECIST version 1.1. * ECOG performance status of 0-1 * Adequate organ function, including: Hematologic function; Hepatic function; Renal function (no strict upper/lower limit required); * Patients must be considered potential candidates for a kidney-preserving treatment strategy, including: Absolute or relative indication for renal preservation (e.g., solitary kidney, baseline renal insufficiency), or Strong preference for kidney preservation after multidisciplinary discussion * Ability to understand and willingness to sign written informed consent. Exclusion Criteria: * Evidence of distant metastatic disease (M1). * Unresectable or bulky nodal disease (≥N2) not amenable to curative-intent surgery. * Prior systemic therapy for urothelial carcinoma, including:Chemotherapy; Immunotherapy; HER2-targeted therapy. * Prior radical nephroureterectomy for current disease. * Active autoimmune disease requiring systemic treatment within the past 2 years. * Current use of immunosuppressive medication, excluding physiologic doses of corticosteroids. * Uncontrolled intercurrent illness, including but not limited to: Active infection requiring systemic therapy; Uncontrolled cardiovascular disease; Significant pulmonary disease * Known active hepatitis B, hepatitis C, or HIV infection with uncontrolled viral replication. * History of another malignancy within the past 5 years, except: Adequately treated basal cell carcinoma; Squamous cell skin cancer; In situ carcinoma. * Pregnant or breastfeeding women. * Any condition that, in the opinion of the investigator, would interfere with study participation or interpretation of results.