Phase II Clinical Trial of Interactive MR Imaging–guided Interstitial Radiofrequency Thermal Ablation of Primary Kidney Tumors: Initial Experience

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Abstract
To perform a phase II clinical trial to evaluate efficacy and safety of interactive magnetic resonance (MR) imaging-guided radiofrequency (RF) interstitial thermal ablation (ITA) of primary renal tumors. Ten male patients (age range, 25-83 years) with peripheral renal cell carcinoma and contraindications to surgery were treated with percutaneous RF ITA entirely guided and monitored with a 0.2-T MR imaging unit. By using a 200-W RF ablation system and custom-fabricated MR imaging-compatible cool-tip electrodes, pulsed RF current was applied for single or multiple ablation cycle(s) of 12-15 minutes until the entire tumor was replaced by an enlarging zone of low signal intensity on T2-weighted and/or short inversion time inversion-recovery images acquired intermittently during the procedure. Kidney MR images were acquired before, immediately after, and 2 weeks after ablation and then every 3 months for 1 year and every 6 months thereafter. Intra- and postprocedural complications were assessed with clinical evaluation of patients for pain and hemodynamic instability and evaluation of MR images for evidence of hemorrhage or other unexpected findings. Follow-up images were assessed for delayed complications such as renal ischemia, infarct, urinoma, or tumor recurrence. Treated tumors ranged between 0.63 and 16.90 mL in volume and 1.0 and 3.6 cm in maximum diameter. Successful RF electrode insertion and/or repositioning into the renal mass was achieved in all cases with direct MR "fluoroscopic" guidance. Thirty ablation cycles were conducted at 21 electrode positions in the 10 procedures, and complete ablation, as defined with MR imaging, was achieved in all cases by the end of the procedure. Apart from two small self-limited perirenal hematomas, no intra- or postprocedural complications were observed. No delayed complications or tumor recurrence occurred during a mean follow-up period of 25 months +/- 9.4 (standard deviation). Although these results are preliminary, interactive MR imaging-guided RF ITA for treatment of primary renal tumors has a high success rate.