This clinical trial aims to compare the effectiveness and safety of two treatment options for patients with high-risk upper tract urothelial carcinoma (UTUC). One group will receive neoadjuvant chemotherapy with gemcitabine and cisplatin followed by surgery (radical nephroureterectomy), while the other group will undergo surgery without chemotherapy. The primary goal is to assess the pathological response to treatment, focusing on how much the tumor shrinks before surgery. The trial will also evaluate the safety of the treatments, overall survival, and recurrence-free survival. This study will help determine whether adding chemotherapy before surgery improves outcomes for patients with high-risk UTUC.