ENDOUROLOGY & LAPAROSCOPY

Incomplete renal tumor destruction using radio frequency interstitial ablation
Michaels MJ, Rhee HK, Mourtzinos AP, Summerhayes IC, Silverman ML, Libertino JA
From the Departments of Urology and Pathology, Lahey Clinic
Burlington, Massachusetts, USA
J Urol. 2002; 168:2406-10

• Purpose: We evaluate the efficacy of temperature based radio frequency ablation as a potential treatment modality for small (less than 3.5 cm) renal tumors.
• Materials and Methods: We treated 15 patients with a total of 20 tumors with radio frequency ablation through an open surgical approach immediately before partial nephrectomy. All tumors were biopsied before radio frequency ablation treatment. Tumors were heated to 90 to 110C for 6 to 16 minutes (mean 9.1). Tumor ablation was monitored by direct vision and ultrasound. Partial nephrectomy was performed in standard fashion. All specimens were stained with hematoxylin and eosin, and 5 specimens were stained for nicotinamide adenine dinucleotide (NADH) diaphorase activity.
• Results: Tumors ranged from 1.5 to 3.5 cm. (mean 2.4) in greatest dimension. All 20 specimens had evidence of morphologically unchanged tumor and normal renal parenchyma on standard hematoxylin and eosin staining. Of the 5 specimens 4 stained positively for NADH in areas confirmed to be tumor in hematoxylin and eosin stained neighboring sections. There was 1 intraoperative renal pelvic thermal injury requiring pyeloplasty and 2 postoperative caliceal leaks requiring stent placement.
• Conclusions: In our series radio frequency therapy did not result in total tumor destruction when specimens were examined with hematoxylin and eosin or NADH staining. We believe that radio frequency interstitial tumor ablation of renal cell carcinoma without subsequent tissue resection should continue to be an investigational treatment modality for those who would otherwise undergo partial or radical nephrectomy.
  
  
• Editorial Comment
  In many ways, the kidney would seem to be a wonderful organ to which to apply “needle-invasive” or extracorporeal therapy for malignancies. It is fairly consistently oriented, it can be accessed through a pathway (the retroperitoneum) that avoids any vital organs, and it is easily imaged. Moreover, malignancies in the kidney are more often being detected when they are small, and therefore more amenable to these minimally invasive techniques. Finally, urologists have long had a close working relationship with radiologists, who are the ones in many institutions who control the mechanisms used in the application of these techniques. It is not surprising, then, that there has been such great interest in “needle-invasive” or extracorporeal treatments for renal masses suspicious for malignancy. This article throws a bit of caution back to the enthusiasts of one of the emerging techniques, radio frequency ablation. In their series of 15 patients with 20 tumors, treated with an open surgical application of radio frequency ablation immediately prior to partial nephrectomy, there was incomplete tumor destruction as assessed by HE staining in all 20 tumors. As this stain may overestimate the viability of cells immediately after thermal coagulation, the authors assessed the histology with NADH stain in the last 5 tumors. NADH stain evaluates for enzymatic activity that may more accurately determine viability of the cells. With this stain, however, 4 of 5 specimens still appeared to have incomplete tumor destruction. Looking at the varied results of radio frequency ablation for renal tumors that have been reported in the literature, one obvious conclusion is that the technical aspects of the procedure are critical and not yet completely defined. Results from reputable institutions have varied from excellent to, as in this article, poor. It might be that these investigators’ open surgical application was based more on misleading visual needle localization than radiographic localization. Some might argue that the parameters of the treatment were not optimal. Alternatively, it may be that these authors’ assessment methods were in fact more accurate than those of others were, and that is the reason for their poor (more accurate) results. Whatever the reasons for the extreme variations, it is certain that the answer is not going to be easily attained. With this degree of variation and uncertainty, I agree with the authors that radio frequency ablation of renal masses suspicious for malignancy should still be considered investigational at this time.

Dr. J. Stuart Wolf Jr.
Associate Professor of Urology
University of Michigan
Ann Arbor, Michigan, USA