BERKELEY, CA (UroToday.com) - More than 8 years ago, Dr. Christos Georgiades and I met to discuss a potential collaboration between interventional radiology and urology to advance a formal program in percutaneous renal cryoablation for small renal masses. At the time, there was much consternation from both communities about such an interaction, and concerns about potential "turf battles" and appropriate oversight for proper cancer surveillance follow-up. In addition, there was significant concern whether or not ablation was as efficacious as partial nephrectomy. That concern culminated in an AUA guideline for management of the clinical stage 1 renal mass, in 2009. The AUA guideline was a consensus (expert committee) meta-analysis document culled from 114 articles, and it concluded that ablation was inferior to partial nephrectomy in long-term outcomes. However, at the time of the analysis, there was a paucity of data from renal cryoablation studies, and most of the early studies lacked long-term outcomes reported in oncological terms (e.g., recurrence-free survival, cancer-specific survival, and overall survival). In addition, most early studies either lacked sufficient patients to look at long-term outcomes, or were combined among many different providers and institutions.
This series constitutes the outcomes of patients who were jointly treated and followed Dr. Georgiades and me in a prospective fashion. The series began after previous experience with laparoscopic and CT guided ablation done by urologists not formally trained in IR. This prior experience (over the prior 7-8 years) was invaluable in setting guidelines for patient selection. This arrangement also allowed for thoughtful and honest discourse for both strategy in treatment and reading and interpreting subsequent scans. Unlike most centers whose primary focus was on the minimally invasive component of this treatment -- and hence tended to use the least number of cryoablative probes possible to completely cover the lesion -- our focus was on oncological success, and therefore we settled on the use of a sufficient number of cryoablative probes to ensure a cytotoxic margin around the tumor, typically in the range of 1 cm from the ice edge, and no less than 5 mm. We also settled on the use of a 2.4 mm cryoablative probe as the standard probe, as it had the best ratio of size to ablation zone, and could be easily combined to generate variable geometry capable of fully ensuring a successful ablation around the lesion. We carefully monitored ablation data and noted temperature drops around vessels were different than non-vascular tissue. We also carefully studied the anatomy to ensure that neighboring structures were protected. We noted that ablations near the ureter tended to cause ureteral strictures, but could be fully protected with a ureteral stent. We also noted that ablations near the adrenal gland results in arrhythmias, which could also be protected by peri-ablation beta blockade. Finally, we noted that tumors near the genito-femoral nerve or intercostal nerves could result in a neuropraxia/neuralgia but could be avoided by appropriate placement of probes to avoid these structures, or advising laparoscopic ablation or partial nephrectomy if those structures could not be avoided. The culmination of these efforts was a sustained larger series of patients with very careful long-term follow up and uniform treatment and follow up parameters. This paper reports the five-year oncological outcomes of that effort and demonstrates that when renal cryoablation is done in a systematic and careful manner, with an experienced interventional radiology and urologist working together, the results can be comparable to extirpative surgery. With the advance of robotic partial nephrectomy, there is increasing desire to perform partial nephrectomies on patients with small renal masses, even when less invasive alternatives are available. However, warm ischemic times from clamping renal vessels often cause irreversible injury to the entire kidney, whereas cryoablation rarely has impact on renal function.
As longer-term data matures on cryoablation of renal masses, we would recommend that the 2009 guidelines for the AUA be revised and the concepts revisited with a larger data set.
Ron Rodriguez, MD, PhDa with Christos Georgiades, MD, PhDb as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
aHenry B. and Edna Smith Dielmann Memorial Chair in Urologic Science, Professor and Chairman, Department of Urology, University of Texas Health Science Center San Antonio, San Antonio, TX USA
bDirector, Interventional Radiology, American Medical Center, Cyprus