Irreversible Electroporation for the Treatment of Small Renal Masses: 5-Year Outcomes - Beyond the Abstract

Irreversible electroporation (IRE) is a novel Food and Drug Administration-approved technology that utilizes high-voltage, short-pulse electrical currents to athermally ablate soft tissue. Multiple electrode probes are placed in an image-guided fashion into target tissues, and the application of energy across the probes results in cellular membrane pores and induces apoptosis. Within the field of urology, this has been applied to focal ablation of prostate cancer and treatment of small renal masses.


Due to its mechanism of action, IRE is less affected by the “heat sink” effect that currently limits successful ablation with biopsy-proven renal cell carcinomas (RCC) (RFA) or cryoablation of some small renal masses near the renal hilum or collecting system. Moreover, it has been demonstrated to spare more connective tissue, blood vessels, and nerves during ablation, potentially minimizing pain and allowing safe treatment of tumors that are more centrally located and adjacent to the bowel. Prior studies have demonstrated the feasibility of IRE for the ablation of small renal tumors, but the current literature has been limited to small studies with short-term follow-up. To date, there have been no published studies regarding the intermediate-term oncologic efficacy of this treatment modality for small renal masses.

In this study, we evaluate intermediate-term functional and oncologic outcomes for a cohort of 48 tumors in 47 patients that were treated with IRE. Among these, 45.8% were biopsy-proven renal cell carcinomas (RCC). There were no complications ≥ Clavien grade 3 related to treatment. Initial treatment success was 91.7%, and treatment failures were managed with salvage RFA or robotic partial nephrectomy. All of the early treatment failures were early in our institutional experience and related to the learning curve of IRE; this is a technically demanding procedure, with each probe placed in a precisely parallel configuration at the same death in order to adequately bracket the tumor for treatment.

About 60% of patients treated with IRE ultimately experienced a decline in glomerular filtration rate from pre-operative baseline (median decline of 11, IQR 7-18), and 18.2% of patients were re-classified to a higher stage of chronic kidney disease in follow up. Though this decline over time may be related to underlying co-morbidities such as hypertension, diabetes, or atherosclerosis (which may contribute as well to patient selection for a non-surgical treatment modality) and may not be clinically significant for all patients, it is notable that these rates are more than double those reported for chronic kidney disease upstaging at 4 years among those undergoing cryoablation for a renal mass. Longer-term renal functional outcomes should be carefully considered in this population of patients that are likely to already suffer from a higher comorbidity burden.

The median follow-up time in our study was 50.4 months. For all patients, the 5-year local recurrence-free survival (LRFS) was 81%, metastasis-free survival (MFS) was 97.1%, and overall survival (OS) was 90.6%. For those with biopsy-proven RCC, these rates were 81.4%, 93.3%, and 92.3%, respectively, at 5 years. Cancer-specific survival at 5 years was 100%. Overall, the patients with local recurrence had small tumor sizes, favorable polar locations, and low-complexity nephrometry scores, suggesting that recurrences may result from the technical limitations of IRE, rather than tumor-specific characteristics. Moreover, when compared to historical 5-year LRFS and MFS for RFA or cryoablation, oncologic outcomes of IRE at 5 years remain inferior.

Though this was a single-center retrospective study, to date it represents the largest cohort of patients with small renal masses treated with IRE with the longest duration of follow-up. Our study indicates that despite safety and feasibility, there are significant limitations to IRE as a treatment modality for small renal masses in both functional and oncologic outcomes over the intermediate-term, which remain inferior to current ablative technologies. Moreover, ours is a high-volume tertiary care center with significant experience in renal mass ablation, and one might expect even less optimal outcomes in centers with less experience in IRE or ablative technologies. Given these findings, we believe IRE should be restricted only to very select cases.

Written by: Jessica C. Dai, MD, Tara N. Morgan, MD, Jeffrey A. Cadeddu, MD, Urology Department at UT Southwestern Medical Center, Dallas TX

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