Andrew Hines-Peralta

Review of Radiofrequency Ablation for Renal Cell Carcinoma

This review will discuss how minimally invasive, image-guided radiofrequency (RF) tumor ablation [i.e., coagulating tumor using short-duration heating (<15 minutes) by directly applying temperatures >50°C via needle electrodes] is being incorporated as a clinical tool for the treatment of renal cell carcinoma. RF ablation has been used to treat focal liver tumors. Potential benefits of this thermal therapy include reduced morbidity and mortality compared with standard surgical resection and the ability to treat nonsurgical patients. More recently, this technique has been introduced to treat focal renal tumors, particularly incidental lesions smaller than 3 cm in elderly patients and those with comorbid conditions. Other uses have included treatment in patients with von Hippel-Lindau syndrome and other diseases that predispose patients to multiple renal carcinomas, where renal parenchymal preservation is desired. Techniques, complications, and results will be discussed. Additionally, strategies that we are currently studying to improve RF outcomes and enable the potential treatment of larger tumors will be addressed. Most notably, recent data on increased coagulation achieved by combining RF ablation with antivascular/antiangiogenic therapies, such as arsenic trioxide, that reduce blood flow and promote heat retention are provided.

Hybrid Radiofrequency and Cryoablation Device: Preliminary Results in an Animal Model

PURPOSE To determine whether the simultaneous application of combined bipolar radiofrequency (RF) ablation and cryoablation in a hybrid system produces larger ablation zones than RF or cryoablation alone. MATERIALS AND METHODS Multiple 15-minute ablations were performed in ex vivo bovine liver (n = 167) with a hybrid applicator system with RF ablation alone (0.3-0.7 A), cryoablation alone (3,500 psi, two freeze/thaw cycles), and combined RF/cryoablation (0.4-0.7 A, 1,000-3,500 psi) with use of a novel applicator consisting of two 2.5-cm active bipolar RF poles located on the same 18-gauge needle separated by two embedded cryoablation nozzles. Resultant coagulation diameters were compared with use of analysis of variance for more than three groups or Student t tests for two groups. Confirmation of the optimal parameters of combination RF/cryoablation was performed by reassessing a range of argon pressure (1,000-3,500 psi) and RF current (0.4-0.7 A) in in vivo porcine liver (n = 36). Arrays of two to four RF/cryoablation applicators were also assessed in ex vivo (n = 54) and in vivo (n = 12) liver. RESULTS In ex vivo liver, simultaneous RF/cryoablation (0.6 A, 3,000 psi) produced 3.6 cm +/- 0.4 of short-axis coagulation. This was significantly larger than that achieved with optimal RF alone or cryoablation alone (1.5 cm +/- 0.3 and 1.6 cm +/- 0.3, respectively; F = 95; P < .01). The coagulation diameter with simultaneous combination RF/cryoablation was related in parabolic fashion to argon pressure and current with a multivariate r(2) of 0.68. For in vivo liver, optimal combination RF/cryoablation achieved 3.3 cm +/- 0.2 of coagulation, which was significantly larger than that achieved with RF alone (1.1 cm +/- 0.1; P < .01) or cryoablation alone (1.1 cm +/- 0.1 and 1.3 cm +/- 0.1; F = 203; P < .01). The greatest contiguous coagulation was achieved with multiple-applicator arrays. For ex vivo liver, short-axis coagulation measured 5.3 cm +/- 0.1, 6.4 cm +/- 0.1, and 7.6 cm +/- 0.1 for two-, three-, and four-applicator arrays, respectively. For in vivo liver, two-, three-, and four-applicator arrays produced 5.1 cm +/- 0.2, 5.8 cm +/- 0.5, and 7.0 cm +/- 0.5 of confluent coagulation, respectively. CONCLUSION Simultaneous combination RF and cryoablation with use of a novel applicator design yielded significantly larger zones of coagulation than either modality alone. The large ablation diameters achieved warrant further investigation of the device.

Chemical tumor ablation with use of a novel multiple-tine infusion system in a canine sarcoma model.

PURPOSE To determine whether larger confluent zones of ablation can be achieved in chemical ablation with use of a multiple-tine infusion device compared with standard needle infusion in a solid tumor model. MATERIALS AND METHODS Multiple canine venereal sarcomas (N=42) were implanted in nine mildly immunosuppressed dogs (treated with 10 mg/kg cyclosporin A twice daily). Tumors incubated for 8-12 weeks grew to a diameter of 5.4 cm+/-1.0. With ultrasound guidance, 8-56 mL of 100% ethanol or 15% acetic acid (diluted in saturated saline solution) were injected in aliquots (2-8 mL) at multiple distances (radius of 0-2 cm) from the needle axis with use of a multiple-tine infusion device. Presence of fluid reflux at the needle puncture site and resultant coagulation diameters were measured within 1 hour and compared with the results of infusion with a standard 18-gauge needle. RESULTS Multiple-tine infusion enabled greater fluid infusion (15 mL+/-3 to 53 mL+/-3 depending on protocol) than standard needle injection (8 mL+/-1) before reflux was observed at the puncture site (P<.01). Additionally, progressive gains in contiguous tumor coagulation were achieved because acetic acid was infused as far as 2 cm from the needle axis with the multiple-tine device (P<.01; R(2)=0.59; y=0.5x+2.9). Optimal coagulation was achieved with the infusion of 4-mL aliquots at 0.5 cm and 1.0 cm from the needle, followed by three 4-mL or 8-mL aliquots (40 degrees rotation between infusions) at 1.5 cm and 2.0 cm from the needle (32 mL+/-0 and 53 mL+/-3 total, respectively). This yielded confluent short-axis coagulation diameters of 4.9 cm+/-1.0 and 5.4 cm+/-1.0, respectively, which were significantly greater than the measurement of 3.1 cm+/-0.4 achieved with standard needle infusion (P<.01). Smaller and noncontiguous foci of coagulation foci (1.7 cm+- 0.5) were seen with the use of ethanol for standard needle and multiple-tine infusions. CONCLUSIONS Chemical ablation with 15% acetic acid with use of a multiple-tine infusion device resulted in larger diameters of contiguous tumor coagulation and enabled greater volumes of infusion than standard needle infusion or ethanol ablation. This suggests that chemical ablation with acetic acid infused with use of a multiple-tine device may overcome some of the difficulties seen with the use of conventional needle chemical ablation injection alone, such as irregular ablation and fluid reflux up the needle tract.

Radiofrequency Ablation and Cryoablation for Renal Cell Carcinoma

Percutaneous tumor ablation has become one of the most prevalent treatment options for small renal cell carcinomas given continued favorable outcome, and is already a treatment of choice for selected patients. Currently, the most common indications are elderly patients with small incidental tumors of unclear metastatic potential, and high-risk surgical patients since this procedure has been shown to be safe in patients with multiple co-morbidities. This chapter describes the indications, applicators, procedure, outcomes, and complications of percutaneous tumor ablation of renal cell carcinoma. Importantly, the technologies are continuously improving and it is expected that patient selection and satisfaction will continue to expand and outcomes will continue to improve.