Abstract
PURPOSE: To investigate the safety and efficacy of ureteroscopic cryoablation by a liquid-nitrogen system in a porcine model and for patients with upper tract urothelial carcinoma (UTUC) of a solitary kidney. METHODS: In the animal experiment, the right-sided ureter was frozen in nine pigs. Eight were randomly assigned to two different groups according to the freezing duration of 60 or 90 s. The other one was designed to receive a 10-min freeze. The treated ureters were harvested at 30 min, 2 days, 4 weeks, and 3 months after cryoablation for histological evaluation. After the animal study, we conducted a pilot clinical trial that enrolled six patients who were diagnosed with UTUC of a solitary kidney and received therapeutic management with ureteroscopic cryoablation at our center. Perioperative adverse events and oncological outcomes were evaluated. RESULTS: In the porcine model, the liquid-nitrogen system was capable of forming a therapeutic ice ball which infiltrated the full-thickness ureter and induced apoptosis and necrosis from mucosa to lamina muscularis through histological examination. In the clinical trial, cryoablation was successfully performed under ureteroscopy in all the patients, without intraoperative ureteral perforation, avulsion, or active hemorrhage. No recurrence in situ was observed during a median follow-up period of 12.5 months. Hydronephrosis and ureteral stricture was observed in one patient and was managed with ureteroscopic balloon dilation. CONCLUSIONS: Ureteroscopic cryoablation induced by liquid nitrogen is a promising technique for conservative management of UTUC with benefits of improving local tumor control and preservation of a solitary kidney.