⁃ Must be aged 19 years or more

⁃ Must have histologically or cytologically proven UTUC arising from renal pelvis and/or ureter.

⁃ Must have histological evidence of high-risk muscle-invasive disease (i.e., pT2\

• T4) and/or N+ disease.

⁃ Must have an ECOG performance status of 0 to 1

⁃ Received at least 3 or 4 cycles of adjuvant cisplatin-based chemotherapy, and proved to have no evidence of disease recurrence with imaging studies, urine cytology and cystoscopy

⁃ At least 3 weeks since the last surgical procedures or chemotherapy prior to enrolment. Subjects must have recovered to \<Grade 2 from all acute toxicities or toxicity must be deemed irreversible by the investigator.

⁃ Adequate marrow function without growth factor support or transfusion dependency A. Neutrophil 1,500 cells/μL or more B. Platelet count 100,000/μL or more C. Hemoglobin 9.0 g/dL or more

⁃ Adequate renal function with serum creatinine 1.5 x ULN or a calculated creatinine clearance ≥ 50 mL/min using the CockcroftGault or MDRD formulas

⁃ Adequate hepatic function A. Bilirubin 1.5 times upper limit of normal (x ULN) or less; does not apply to subjects with Gilbert's syndrome diagnosed as per institutional guidelines. B. AST (SGOT) and ALT (SGPT) 3 x ULN or less; if liver metastases are present, then 5 x ULN is allowed.

⁃ Women of childbearing potential must use effective contraception continuously for at least 30 days after the final dose of avelumab. At least one method classified as highly effective (failure rate \< 1%) must be employed (see Table 1).

⁃ Written and voluntary informed consent understood, signed and dated.

⁃ Negative serum or urine pregnancy test at screening for women of childbearing potential.