Cryoablation safe, effective in treating suspicious masses in solitary kidneys

Nephron-sparing surgery has become the mainstay of treatment for small renal masses in solitary kidneys. While long-term oncologic control and preservation of renal function is well established for partial nephrectomy and laparoscopic partial nephrectomy, new data in patients treated with ablative technology are just emerging.

Researchers from Columbia University, New York, and the University of North Carolina, Chapel Hill, presented the results of a series of 32 patients with solitary kidneys who underwent either percutaneous or laparoscopic ablation for suspicious renal masses between 2006 and 2008.

The researchers reviewed their prospectively collected cryoablation databases of the two institutions and looked specifically at patients with solitary kidneys. Over the 2-year period, 32 patients with solitary kidneys were treated with cryoablation. Average patient age was 62 years, and mean lesion size was 2.2 cm.

The procedure was performed laparoscopically in 18 patients and percutaneously in 14 patients. Biopsy was performed in all patients at the time of cryoablation and was diagnostic in all but one patient. In all, 66% of patients had variants of renal cell carcinoma, while 33% had benign lesions.

Most of the benign lesions were oncocytomas, Dr. Okhunov noted.

The procedure was performed either laparoscopically or percutaneously depending on the size, location, and surrounding anatomy of the lesion. Cryoprobes were inserted directly into the tumor, and cryoablation was performed using two freeze-thaw cycles. In this study, the first and second freeze cycles averaged 14 and 9 minutes, respectively. Patients were then followed with CT scans to assess for residual enhancement of the treated lesions.

To follow renal function, the researchers examined postoperative serum creatinine, which Dr. Okhunov said "was difficult because several patients were lost to follow-up after 1 year." But at 1 year, the researchers did not detect a drop in renal function.

"Renal function appears to be preserved in this challenging population," he said.

Low recurrence rate

The study also demonstrated promising oncologic results. Of the 32 patients treated, none had incomplete ablation as determined by the first CT scan following surgery.

"We consider enhancement on CT prior to 6 months to be an incomplete ablation, whereas enhancement after 6 months is considered recurrence," Dr. Okhunov explained.

Two patients had recurrent enhancement at greater than 6 months after surgery, both of whom were successfully treated with re-ablation. This was accomplished with a minor complication rate of 9.4% and without any major complications. In addition, the average length of stay in the hospital was 0.5 days.

Although the authors admit that longer-term follow-up with a larger number of patients is necessary in order to assess the functional and oncologic outcomes of cryoablation, these early results are promising and support a role for ablative therapy as an effective, low-morbidity option for treating small renal tumors without putting patients at risk for end-stage renal disease.

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