Cryo is superior to HIFU, RFA in small renal tumors

October 15, 2006

Cleveland-For now, laparoscopic cryoablation appears to be more effective than both radiofrequency (RF) ablation and high-intensity focused ultrasound (HIFU) in the treatment of small renal tumors, a group of Austrian researchers reported here at the 2006 World Congress of Endourology.

Cleveland-For now, laparoscopic cryoablation appears to be more effective than both radiofrequency (RF) ablation and high-intensity focused ultrasound (HIFU) in the treatment of small renal tumors, a group of Austrian researchers reported here at the 2006 World Congress of Endourology.

"All of these minimally invasive, energy-ablative techniques are experimental, to one degree or another, but it seems cryotherapy is the most effective at this point," said Hans-Christoph Klingler, MD, professor of urology at the Medical University of Vienna. "There is still quite a bit of work to do with each of them in terms of getting techniques more refined and reliable."

Forty-two patients were included in the study: 17 who had renal tumors <4 cm underwent RF ablation with a 1500X RF System (RITA Medical Systems, Fremont, CA) and subsequent laparoscopic partial nephrectomy, while another 16 were treated with HIFU using a prototype device by Storz Medical (Tägerwilen, Switzerland), and nine received cryoablation using the Seednet (Oncura Inc., Plymouth Meeting, PA).

Weighing results, potential

"We were a little surprised that the RFA results weren't as good as we had hoped," said Dr. Klingler. "But all of these procedures must be weighed against the standard of care: open or laparoscopic removal of the tumor. We have to be open-minded with these new, sometimes experimental treatments because, in the long run, I think we'll see refinement of the technology to the point that they might rival the current gold standard."

Another problem with RF ablation was that of "skipping." Because tumor tissue composition is not uniform and because some areas of tumor are better vascularized than others, electrical current associated with RF ablation will sometimes skip to areas of the tumor with less impedance.

"That leaves some areas without proper treatment and renders RFA somewhat unreliable," Dr. Klingler explained. "And in a portion of these patients, it was unclear whether the oncological efficacy of RFA could be proven. There was some remaining tumor tissue, which is always cause for worry when it comes to efficacy."

HIFU-treated patients had the largest mean tumor size in the study (46 mm vs. 35 mm for cryotherapy patients and 27 mm for RF ablation patients). HIFU also required the longest operative time of the three methods: 120 minutes.

Dr. Klingler noted that HIFU was considered the most "experimental" therapy used in the study.

"The HIFU machine we used was designed for percutaneous therapy, but we didn't want to use it with curative intent," Dr. Klingler said. "So we chose patients who agreed to undergo HIFU therapy prior to laparoscopic nephrectomy simply to analyze how well the device worked.

"However, of the three techniques we studied, HIFU may have the most future potential. Cryotherapy produces the most reliable results in terms of oncological efficacy, but this needs to be confirmed with long-term results. RFA is an option only for small renal tumors, which may not be highly vascularized."

Dr. Klingler characterized HIFU as "a very safe treatment, since high temperatures generated within a tiny, focused area will provide reliable oncological efficacy. The main disadvantage is that targeting the tumor is difficult; therefore, we were not able to cover the entire tumor in the majority of cases."

Two cycles of cryotherapy were administered after a specimen biopsy had been obtained. Surgical time was about 1 hour, with mean blood loss of 70 mL. Eight of the nine patients treated with cryoablation were found to have renal cell carcinoma; the ninth patient had a benign tumor.

All specimens in the study were evaluated by frozen section and standard histology. Follow-up included serum creatinine, renal ultrasonography, and helical contrast-enhanced CT scan or MRI at 3, 6, 12, and 18 months. Mean follow-up times were 11 months for RF ablation and 4 months for cryotherapy. No mean follow-up time was available for HIFU.