643 JOURNAL OF ENDOUROLOGY Volume 19, Number 6, July/August 2005 © Mary Ann Liebert, Inc. Treatment of Renal Tumors with Radiofrequency Ablation ANDREW A. WAGNER, M.D., STEPHEN B. SOLOMON, M.D., and LI-MING SU, M.D. ABSTRACT Background: Radiofrequency (RF) energy has been investigated as a minimally invasive modality for ablat- ing small renal tumors. Recent advances in the application of this technology have improved its safety and effectiveness. Materials and Methods: We describe the technology of RF application and review the current delivery sys- tems as applied to renal tumor ablation. We also review relevant animal studies, which have revealed the nat- ural history of ablated renal tissue. Finally, we examine recent human trials with an emphasis on longer-term follow-up, imaging, complications, and successful ablation according to tumor location within the kidney; i.e., central v peripheral. Results: Radiofrequency ablation can be performed safely in a minimally invasive fashion either percuta- neously or laparoscopically. Energy delivery varies, and available systems include dry, wet, cooled-tip, and bipolar electrodes. Heat rise and subsequent charring in the tissue adjacent to the electrode is limited by tem- perature or impedance-based feedback systems. In animal studies, ablation results in complete cell kill, as judged by nicotinamide adenine dinucleotide diaphorase staining. Clinical trials with intermediate follow-up show excellent success rates. Tumors 3 cm and central tumors have a higher recurrence rate after RFA than smaller, more peripheral tumors. Conclusions: The current literature suggests that RFA is a promising minimally invasive method of treat- ing small renal tumors. Nevertheless, long-term follow-up is still required, and questions remain regarding the optimal delivery system, duration of ablation, and method of surveillance. INTRODUCTION T HE ROUTINE USE of abdominal imaging has increased the detection of renal tumors. In fact, in the United States, it was projected that 31,900 new cases of renal cancer would be discovered in the year 2003. 1 Most of these tumors are small, being found incidentally by CT for unrelated symp- toms. 2 Despite their relatively slow growth rate, careful con- sideration of definitive treatment is necessary, because as many as one third of these tumors may have fast doubling times and therefore pose a risk of progression and metasta- sis. 3 Open and laparoscopic partial nephrectomy are estab- lished approaches to these tumors; however, many of these patients are older or have multiple risk factors, making them poor operative candidates. Laparoscopic renal cryoablation has been performed since the mid-1990s, with excellent mid- term results. 4,5 Radiofrequency ablation (RFA), delivered la- paroscopically or percutaneously, has also been introduced as an alternative for renal tumors following the successful treatment of liver, bone, breast, endometrium, pancreas, and prostate lesions. 6 Heat has been used to destroy tissue in urology for more than 90 years, since Edwin Beer reported on his use of current to ablate two large bladder tumors causing hematuria. 7 Radiofre- quency ablation uses alternating current to bring about resistive heating in the area immediately surrounding an electrode and conductive heating of neighboring tissue. This in turn causes cell death, ischemia, and, eventually, coagulation necrosis. The electrodes can create enough heat to ablate solid tumors of the liver and kidney, as stated above, or be used to create very small and precise lesions, as when treating varicose veins or aberrant conductive pathways in the heart. 8,9 Department of Urology, Johns Hopkins Medical Institutions, Baltimore, Maryland.