Irreversible electroporation (IRE) is a nonthermal ablative technology that applies high voltage, short pulse electrical current to create cellular membrane nanopores and ultimately results in apoptosis. This is thought to overcome thermal limitations of other ablative technologies. We report 5-year oncologic outcomes of percutaneous IRE for small renal masses.
A single-institution retrospective review of cT1a renal masses treated with IRE from 4/2013 – 12/2019 was performed. Those with <1 month follow up were excluded. IRE was performed with the NanoKnife© System (Angiodynamics, Latham, NY). Renal mass biopsy was obtained prior to or during ablation in most circumstances; biopsy was excluded in some patients due to concern for IRE probe displacement. Post-ablation guideline-based surveillance imaging was performed. Initial treatment failure was defined as persistent tumor enhancement on first post-treatment imaging. Survival analysis was performed via the Kaplan-Meier method for successfully treated tumors (SPSS; IBM, Armonk, NY).
IRE was used to treat 48 tumors in 47 patients. 22/48 tumors (45.8%) were biopsy-confirmed renal cell carcinoma (RCC). No complications ≥ Clavien Grade III occurred and 36 patients (76.6%) were discharged the same day. Initial treatment success rate was 91.7% (n=44/48); 3 treatment failures were managed with salvage radiofrequency ablation and 1 with robotic partial nephrectomy. Median follow up was 50.4-months (IQR 29.0-65.5). The 5-year local recurrence-free survival was 81.4% in biopsy-confirmed RCC patients and 81.0% in all patients. 5-year metastasis-free survival was 93.3% and 97.1%, respectively, and 5-year overall survival was 92.3% and 90.6%, respectively. 5-year cancer-specific survival was 100% for both biopsy-confirmed RCC and all patient groups.
IRE has low morbidity, but suboptimal intermediate-term oncologic outcomes compared to conventional thermal ablation techniques for small, low complexity tumors. Use of IRE should be restricted to select cases.

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