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.