Laparoscopic renal cryoablation: acute and long-term clinical, radiographic, and pathologic effects in an animal model and application in a clinical trial.

ABSTRACT

OBJECTIVES: To evaluate renal cryosurgery by studying the feasibility of laparoscopic delivery and the radiographic characteristics and histopathologic effects in a porcine model using different freeze cycles. On the basis of the results, a clinical trial of laparoscopic cryosurgical ablation in select patients with clinical stage T1 renal tumors was started. MATERIALS AND METHODS: Twelve kidneys from six farm pigs underwent cryosurgery. Each kidney was treated with two freeze cycles to -180 degrees C. Six kidneys were retroperitonealized, and six were not. An abdominal CT scan was performed at various times to evaluate for the presence of urinoma or hematoma and to monitor lesion changes. Organs were harvested at times ranging from 24 hours to 13 weeks. Radiographic and histopathologic changes were recorded for each time period. Eight patients with small (average 2-cm) exophytic renal masses underwent laparoscopic biopsy and cryosurgical ablation using a 3- or 4.8-mm probe (Cryomedical Sciences Inc., Rockville, MD) for one 15-minute or two 5-minute freeze cycles to a temperature of -180 degrees C to extend the ice ball at least 7 mm beyond the tumor margin. RESULTS: Dense adhesions between the bowel and cryoablated renal tissue were encountered in all non-retroperitonealized kidneys, but no fistula formation was present. The retroperitonealized kidneys had minimal adhesion formation. None of the animals developed a urinary fistula. At 24 hours and 1 week, CT scanning demonstrated an enhancement defect corresponding to the region of the ice ball with no urinoma or hematoma. At 13 weeks, only a nonenhancing cortical defect was seen. At immediate harvest, hemorrhage was noted in the area of the ice ball with a sharp demarcation at the edge of the freeze zone. At 1 week, four distinct zones were seen central necrosis, inflammatory infiltrate, hemorrhage, and fibrosis with regeneration. At 13 weeks, the necrotic tissue had been replaced with a circumscribed area of fibrosis. There were no intraoperative or postoperative complications in the eight patients. The estimated blood loss was 140 mL, and the mean hospital stay was 3.5 days. At a mean clinical follow-up of 7.7 (range 1-18) months and radiographic follow-up of 5 months; there have been no tumor recurrences or significant changes in the serum creatinine concentration. At 24 hours, there was an enhancement defect in the area of the ice ball. The CT images at 13 weeks showed a nonenhancing cortical defect in the area of the ice ball. CONCLUSIONS: Cryosurgery can be readily delivered laparoscopically, creating a discrete lesion at the time of treatment that appears to be consistent over time. In the animal studies, complete tissue necrosis developed in the freeze zone, followed by reabsorption, and by 13 weeks, fibrous tissue had replaced the defect. In the animal and human trials, there were no operative complications, urinomas, hematomas, or bowel or urinary fistulas. Follow-up imaging in human trials revealed a persistent nonenhancing defect in the area of the freeze zone. Long-term clinical follow-up will be necessary to determine the cancer-free survival rate.