Radiofrequency Interstitial Tumor Ablation (RITA) Is a Possible New Modality for Treatment of Renal Cancer: Ex Vivo and in Vivo Experience

Abstract

Small renal tumors are increasingly diagnosed and are frequently treated by nephron-sparing surgery. Tumors can be ablated by radiofrequency (RF) energy, which allows the operator to create very localized necrotic lesions. Radiofrequency interstitial tumor ablation (RITA) has been used in human kidneys in an ex vivo experiment to assess the necrotic lesions produced in a model close to physiologic conditions and then in three patients with localized renal cancer prior to radical nephrectomy. In the ex vivo model, four freshly removed kidneys were treated. Bipolar RF energy was delivered by a generator connected to two needles introduced parallel to each other into the renal parenchyma. A thermocouple was inserted between the two active electrodes. The renal artery at physiologic conditions was maintained at a constant temperature of perfusion of 37 degrees C by a computer-assisted Hot-line monitor. Two lesions were produced in each pole of each kidney including the cortex and the medulla. In an initial human study focusing on safety, feasibility, and pathology, three patients were treated by RITA with bipolar and monopolar energy. One patient with a peripheral 2-cm upper-pole tumor was treated percutaneously under ultrasound guidance with local anesthesia only 1 week prior to surgery. The other patients, with 3- and 5-cm tumors, were treated during surgery under general anesthesia just before nephrectomy. Ex vivo, the maximum temperature at the active needles ranged from 84 degrees C to 130 degrees C with 10 to 14 W applied during 10 to 14 minutes. Lesions were on average 2.2 x 3 x 2.5 cm.3 Microscopic examination showed stromal edema with intensive pyknosis. No damage was seen to adjacent untreated tissue. In the in vivo procedure, tolerance of RTA as an anesthesia-free procedure was excellent. The size of the observed lesions was comparable to the forecast size depending on the needle deployment. No side effects were noted, and no adjacent structures were affected by the RF ablation. These preliminary studies demonstrate the ability of RITA to produce localized extensive necrosis in kidney parenchyma and tumors safely under local anesthesia. Further studies could evaluate this new minimally invasive treatment in small kidney tumors considered for nephron-sparing surgery.

Percutaneous Radio Frequency Ablation of Small Renal Tumors: Initial Results

“…6,12,16,17 Pathological analysis done in 24 hours of renal tumor radio frequency ablation demonstrates pyknosis, stromal edema, and loss of nucleoli and nuclear detail in the treatment zone. 6,18 Later, changes consistent with coagulative necrosis become more apparent.…”

“…7,9 A vast clinical experience has been obtained with radio frequency ablation of liver neoplasms but renal tumor radio frequency ablation is still in infancy. 10,11 Since Zlotta et al introduced radio frequency ablation for human renal tumor in 1997, 12 early results of percutaneous radio frequency ablation as monotherapy for renal tumor have been reported, however, experience is limited. 13,14 Intraoperative radio frequency ablation of 11 small (3 cm.…”

Nephron-sparing percutaneous ablation of a 5 cm renal cell carcinoma by superselective embolization and percutaneous RF-ablation

“…The technical feasibility of RF ablation of the kidney has already been demonstrated in an experimental set up during open surgery [11], during laparoscopy [12], percutaneously under ultrasound control [13], CT-guidance [9], or MR-guidance [14]. Although these studies differ significantly in number of animals, treatment protocols and follow-up periods and, thus, are hardly comparable, no relevant complications were reported.…”

“…To the best of our knowlegde, only four reports on renal RF ablation exist. Zlotta and co-workers [11] reported on a successful, percutaneously performed RF ablation using a bipolar system of a 2 cm upper-pole tumor 1 week prior to surgery, and on ablations of two 3 cm and 5 cm large tumors during surgery before resection. The resulting necrosis per ablation was 2.2 3 2.5 cm in diameter.…”

Magnetic resonance imaging and model prediction for thermal ablation of tissue

“…MAGNETIC RESONANCE IMAGING (MRI) has been used to provide guidance and monitoring during thermal ablation of tissues (1)(2)(3)(4)(5)(6)(7)(8). The ultimate lesion (coagulation) volume has been determined with T2-weighted turbo-spin-echo (TSE) or contrast-enhanced T1-weighted spin-echo (SE) images (9,10).…”