Transitional Cell Cancer of the Renal Pelvis and Ureter

The goal of this prospective clinical trial is to investigate the safety and efficacy of ST-02 (mucoadhesive gemcitabine suspension for pyelocaliceal instillation) to treat Upper Tract Urothelial Carcinoma (UTUC) in participants who have a low-grade tumor. The main questions this study aims to answer are: 1. Can ST-02 effectively eradicate UTUC by 3 months? 2. Is ST-02 safe for patients with UTUC? Participants in this study will receive ST-02, a new formulation with gemcitabine once weekly for six weeks. Gemcitabine is known to be an effective drug in treating urothelial carcinoma. This new formulation will be instilled directly into the upper urinary tract (renal pelvis) and will allow the chemotherapeutic to work locally for an extended period of time. The administration process will be retrograde (via a small catheter inserted up into the kidney, under anesthesia) or antegrade (via a nephrostomy, in the clinic) once weekly for six weeks. Safety and efficacy will be monitored for up to a year after the initial response assessment.