This is a single-center, prospective, non-interventional observational cohort study designed to establish a structured recurrence monitoring platform in Korean patients with high-grade non-metastatic upper tract urothelial carcinoma (UTUC).

Eligible adult patients scheduled to receive neoadjuvant chemotherapy followed by radical nephroureterectomy will undergo circulating tumor DNA (ctDNA) sampling prior to chemotherapy initiation and once between 1-6 months after surgery.

Clinical, imaging, pathological, and longitudinal follow-up data will be prospectively collected to enable long-term monitoring of recurrence and survival outcomes.

The primary objective is to establish a prospective cohort integrating clinical and molecular data to support future translational research and recurrence prediction modeling in UTUC.

Upper tract urothelial carcinoma (UTUC) is an aggressive malignancy with a high rate of recurrence and metastatic progression following definitive surgery. Although circulating tumor DNA (ctDNA) has shown promise for minimal residual disease detection and early recurrence monitoring in urothelial carcinoma, prospective data in UTUC, particularly in Asian populations, remain limited.

This single-center, prospective, non-interventional observational cohort study aims to establish a structured recurrence monitoring cohort in Korean patients with high-grade non-metastatic UTUC. Adult patients with clinical stage cT2-T4, cN0-1, M0 disease who are planned for neoadjuvant chemotherapy followed by radical nephroureterectomy will be enrolled after providing written informed consent.

ctDNA blood samples will be collected prior to initiation of neoadjuvant chemotherapy and once between 1-6 months following surgery. All treatment decisions, imaging evaluations, and follow-up assessments will be conducted according to standard clinical practice without protocol-mandated interventions.

Demographic, clinical, imaging, pathological, treatment, and longitudinal outcome data will be prospectively collected for up to five years. The study is designed as a cohort-establishment platform and does not test a predefined interventional hypothesis. The accumulated data will serve as a foundation for future recurrence prediction modeling and precision oncology research in UTUC.

Inclusion Criteria:

• Age ≥ 19 years

Histologically confirmed high-grade upper tract urothelial carcinoma (renal pelvis and/or ureter)

Clinical stage cT2-T4, cN0-1, M0

Planned neoadjuvant chemotherapy followed by radical nephroureterectomy

ECOG performance status 0-1

Adequate hematologic, hepatic, and renal function

Ability to provide written informed consent

Exclusion Criteria:

• Evidence of distant metastasis (M1)

Contraindication to cisplatin-based chemotherapy

Uncontrolled infection or severe comorbid medical condition

Pregnancy or breastfeeding

Any condition that, in the investigator's judgment, makes participation inappropriate

Adult Korean patients with high-grade non-metastatic upper tract urothelial carcinoma (cT2-T4, cN0-1, M0) who are candidates for neoadjuvant chemotherapy followed by radical nephroureterectomy at a single tertiary referral center.