Acute histologic changes in human renal tumors after cryoablation

Background and Purpose: Cryoablation is a treatment option for some patients with small, exophytic lesions of the kidney. Several investigators have evaluated the effects of cryoablation in normal renal tissue of animals. The purpose of this study was to investigate the tissue changes following cryoablation in human renal tumors. Patients and Methods: We prospectively evaluated patients with solid renal lesions (1.5-1.8 cm) confirmed by CT, MRI, or both. Metastatic work-up for all patients was negative. All lesions were biopsied prior to freezing. Two patients with bilateral renal tumors underwent argon-gas-based CRYOcare System (Endocare, Irvine, CA) treatment via an open approach. A 3-mm cryoprobe was placed directly into each tumor. A single 15-minute freeze preceded an active thaw (helium gas) for each lesion. Iceball dimensions were monitored by intraoperative ultrasonography. Alter successful cryoablation, partial nephrectomy was performed to remove the lesion, and the renal tissue underwent histologic evaluation. Results: The cryoprobes achieved a temperature of -135°C. No bleeding was noted, and there were no intraoperative or postoperative complications with a mean follow-up of 3 months. Histologically, freezing of renal tissue resulted in coagulative necrosis and hemorrhage beyond the boundaries of the lesions. There was a zone of demarcation between the viable and nonviable tissue. Conclusions: In our series, cryoablation was effective in destroying tumor tissue in vivo in human kidneys. Freezing was sufficient to achieve a negative surgical margin. Cryoablation of renal tumor is an alternative to the currently available nephron-sparing surgical techniques. The long-term effect of tumor tissue destruction by cryosurgery requires further investigation.