Irreversible electroporation of small renal masses: suboptimal oncologic efficacy in an early series.

Purpose: To report on the first short-term oncologic outcomes of percutaneous irreversible electroporation for small renal masses.
Methods: Patients with cT1a renal masses treated with irreversible electroporation from April 2013 through December 2016 were reviewed. Small, low complexity tumors were generally selected for irreversible electroporation using the NanoKnife ^® System (Angiodynamics, Latham, NY, USA). Surveillance imaging was performed post-operatively, and survival analysis was completed using the Kaplan-Meier method.
Results: A total of 42 tumors in 41 patients underwent irreversible electroporation. Mean tumor size was 2.0 cm with a median R.E.N.A.L nephrometry score of 5. Twenty-nine patients (71%) were discharged the same day of the procedure and no major (Clavien grade II or higher) intraoperative or post-operative complications occurred. Initial treatment success rate was 93%; our three failures (7%) underwent salvage radiofrequency ablation. With a mean follow-up of 22 months, 2-year local recurrence-free survival was 83% for patients with biopsy confirmed renal cell carcinoma, 87% with biopsy confirmed or a history of renal cell carcinoma, and 92% for the intent-to-treat cohort.
Conclusions: Although with low morbidity, in comparison to extirpation and conventional thermal ablation technologies, irreversible electroporation has suboptimal short-term local disease control results in this series of small, low complexity tumors. Larger series and longer follow-up will determine the durability of this modality.