RecruitingPhase 2Drug trialSeqUential GeMcitabine and MITomycin Treatment for Favorable High-Risk Upper Urinary Tract Urothelial CarcinomaThis Phase II clinical trial, titled "A Phase II Trial of Sequential Gemcitabine and Mitomycin Treatment for Favorable High-Risk Upper Urinary Tract Urothelial Carcinoma (SUMMIT)," aims to evaluate the safety and effectiveness of a combination chemotherapy treatment for patients with favorable papillary high-grade upper tract urothelial carcinoma (UTUC). The study focuses on sequential administration of two drugs, gemcitabine and Jelmyto (a gel-based form of mitomycin), to potentially preserve kidney function and avoid nephroureterectomy (kidney removal), which is the current standard of care for participants with non-endoscopically resectable tumors.