Feasibility and safety of cryoablation on the porcine ureter using a new balloon cryoprobe

Feasibility and safety of trans-biliary cryoablation: Preclinical evaluation of a novel flexible cryoprobe

Cryoablation, as a well-characterized technology, has multifarious clinical applications in solid malignancy. However, trans-biliary cryoablation for malignant biliary obstruction has not been reported yet. Thus, this study aimed to determine the efficacy and safety of trans-biliary cryoablation with a novel CO₂ gas-based flexible cryoprobe in standardized preclinical settings. For fresh porcine liver ex vivo, the freezing efficacy of cryoablation was evaluated by using fresh porcine liver. The real-time CO2 flow rate, freezing temperature and freezing range were examined and the frozen appearance was visualized. In vivo study, acute and chronical effects were investigated by using the models of canine bile duct. Histopathology and laboratory examination were performed. The lowest temperature that the electrode could deliver to the tissue was -60.7 °C. At 60s after freezing, the tissue temperature dropped to -22.6 °C and -4.3 °C at 0.1 and 0.2 cm from the electrode center, respectively. The frozen size was greater in liver tissue ex vivo than that in bile duct tissue in vivo. No biliary hemorrhage, perforation, stricture, obstruction, and adjacent organ injury were observed. With histopathologic examination, acute intercellular vacuoles were observed in the lamina propria adjacent to the lumen. Chronic changes, including uneven coagulative necrosis, fibro-proliferation, inflammatory infiltration and connective tissue thickening were observed in the lamina propria of the all biliary samples. The results demonstrated CO₂ gas-based trans-biliary cryoablation is safe and efficacious. These findings may provide a potential new modality for primary malignant biliary obstruction and malignant obstruction within a biliary stent and contribute to cryoablation of clinical practice.

Ureteroscopic Cryoablation for Patients with Upper Tract Urothelial Carcinoma of a Solitary Kidney: A Porcine Model and Our Pilot Clinical Experience

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.

Supplementary Information

The online version contains supplementary material available at 10.1245/s10434-021-10233-5.