Percutaneous radio frequency ablation of small renal tumors: initial results

Abstract

Purpose: Thermal tissue ablation with radio frequency energy is an experimental treatment of renal tumor. We report early results of an ongoing trial of percutaneous radio frequency ablation for small renal tumors.

Materials and methods: Patients with percutaneously accessible renal tumors were evaluated for radio frequency ablation. Tumors were solid on computerized tomography (CT), 3 cm. or less in diameter and enlarging during at least 1 year. Ablation was performed at the Interventional Radiology suite under ultrasound and/or CT guidance. A 50 W., 460 kHz. electrosurgical generator delivered radio frequency energy via a percutaneously placed 15 gauge coaxial probe. At least 2, 10 to 12-minute ablation cycles were applied to each lesion. Patients were observed overnight before discharge from hospital and reevaluated 2 months later.

Results: A total of 24 ablations were performed in 21 patients with renal tumor, including solid von Hippel-Lindau clear cell tumor in 19 and hereditary papillary renal cancer 2. Most (22 of 24) procedures were performed with patients under conscious sedation. At 2 months postoperatively mean tumor diameter plus or minus standard deviation decreased from 2.4 +/- 0.4 to 2.0 +/- 0.5 cm. (p = 0.001), and a majority of tumors (19 of 24, 79%) ceased to be enhanced on contrast CT. Mean serum creatinine plus or minus standard deviation was unchanged during this interval (1.0 +/- 0.2 mg./dl.). No major and 4 minor complications were encountered, including 2 episodes each of transient psoas pain and flank skin numbness.

Conclusions: Percutaneous radio frequency ablation of small renal tumor is well tolerated and minimally invasive. It will remain experimental until procedural and imaging parameters that correlate with tumor destruction are validated.

Figures

Fig. 1

RITA Model 70 probe used for most of percutaneous ablations. Multiple electrodes are deployed in position for radio frequency treatment.

Fig. 2

Kidney for assessment of tumor location

Fig. 3

Ultrasound guided radio frequency ablation. Probe (bold arrow) has been inserted into center of tumor. Microbubbles are beginning to form around probe electrodes (thin arrows).

Fig. 4

CT before, during and after radio frequency ablation (patient 20, treatment 23). A, after contrast CT 1 month before treatment indicates solid enhancing tumor (difference in HU 54) in lateral aspect of left kidney (black arrow). B, patient in right lateral decubitus position during treatment and probe electrodes are deployed in tumor. C, 2-month followup after contrast CT lesioned area remains visible (white arrow) but no longer enhances (difference in HU 4).

Fig. 5

CT. A, day before radio frequency ablation (patient 7, treatment 8), with 2.2 cm. medullary tumor (black arrow) representing significant pretreatment enhancement (difference in HU 69). B, during radio frequency ablation. C, 2 months after radio frequency ablation. After treatment lesion has decreased in diameter to 1.6 cm. (white arrow) and lost contrast enhancement (difference in HU 4). Cauterized needle track is still visible 2 months after ablating central tumor (white arrow).