The new research, published in CVIR Oncology, pooled nine years of experience from three specialist centers in the United Kingdom, the United States, and Spain. The retrospective analysis drew on a prospectively maintained database of patients treated with percutaneous IRE between May 2015 and October 2024, using the NanoKnife 3.0 System. Every case involved a biopsy-proven renal cell carcinoma that a multidisciplinary tumor board had deemed unsuitable for partial or radical nephrectomy, or for conventional thermal ablation, typically because the tumor pressed against vital structures, sat within a solitary kidney, or the patient carried significant comorbidities.

The cohort comprised 68 patients with a mean age of 66.9 years, harboring 71 tumors with a mean diameter of 2.83 centimeters. These were not simple lesions: the median RENAL Nephrometry score, a standardized measure of anatomical complexity, was 9, placing them among the most challenging tumors treated anywhere. Nearly 58 percent were entirely endophytic, meaning they grew wholly within the kidney’s interior, and almost half were hilar tumors touching the renal artery or vein. Strikingly, 93 percent of the tumors lay less than one millimeter from a vital structure, including the ureter, colon, renal vessels, collecting system, and in rare cases the inferior vena cava, liver, small bowel, or spleen.

IRE works in a fundamentally different way from the radiofrequency, cryoablation, and microwave techniques that dominate image-guided ablation. Rather than heating or freezing tissue, the technology delivers high-voltage electrical impulses through fine needles placed around the tumor under ultrasound or CT guidance. These pulses create irreversible nanopores in the lipid membranes of cancer cells, disrupting cellular homeostasis, causing loss of intracellular contents and ultimately triggering apoptotic cell death. Crucially, the technique spares structures rich in collagen, such as ureters, blood vessels, and bile ducts, because their architecture does not depend on the cellular membranes that the pulses destroy. It also avoids the heat-sink effect, in which flowing blood dissipates thermal energy and undermines ablation near large vessels.

The procedure itself is technically demanding. Patients undergo general anesthesia with deep neuromuscular blockade to ensure complete muscle paralysis, since the electrical pulses would otherwise provoke violent contractions. Interventional radiologists, each with more than a decade of ablation experience, inserted an average of 4.56 monopolar electrodes to bracket each tumor. A test run of 20 pulses per electrode pair confirmed electrical conductivity, allowing adjustment of voltage to keep delivered current between 20 and 40 amperes, before the full treatment of 90 pulses per electrode pair was delivered with cardiac gating. Mean anesthesia time was 107 minutes, and patients typically stayed 1.6 days in hospital.

The headline results were encouraging. Technical success, meaning complete coverage of the tumor by the ablation zone, was achieved in 100 percent of sessions. Primary technique efficacy, defined as no residual enhancing tumor at the one-month scan, was 77.5 percent. While that figure trails some earlier single-center series, the authors emphasize that their tumors were larger and far more complex than those in comparable studies, and efficacy fell significantly as tumor size rose, particularly beyond 3.5 centimeters. Importantly, the modest primary efficacy did not translate into poor long-term cancer control: when residual disease was salvaged with a single additional ablation session, local control reached 95.8 percent, and five-year local tumor progression-free survival stood at 84.4 percent, rising to 81.1 percent at seven years.

Safety data were equally notable. Only two major adverse events occurred among 71 procedures, a rate of 2.8 percent: one permanent ureteric injury requiring long-term stenting and one episode of hematuria that resolved after stent removal. By comparison, published series of cryoablation for completely endophytic tumors report major complication rates approaching 10 percent, and robotic partial nephrectomy series report grade 3 or higher complications of around 17.5 percent. Kidney function was well preserved, with a mean decline in estimated glomerular filtration rate of just 7.5 ml/min/1.73m2, and only 10 percent of patients experiencing a clinically significant drop of more than 25 percent. Oncological durability was also reassuring, with cancer-specific survival of 98 percent at five years and metastasis-free survival of 91 percent.

Perhaps the most striking finding came from the composite ‘trifecta’ outcome, borrowed from surgical practice and combining primary efficacy, absence of major complications, and less than 25 percent decline in kidney function. IRE achieved the trifecta in 68.6 percent of cases, exceeding the 58.8 percent reported for thermal ablation and the 65.3 percent for robotic partial nephrectomy in comparable multicenter analyses of endophytic tumors. The authors suggest this may reflect IRE’s inherent suitability for tumors hugging critical structures, though they caution that head-to-head prospective comparisons are still needed before declaring superiority. They also describe practical refinements, including placing the electrode nearest a vital structure as the anode so pulses fire away from it, and using pre-operative ureteric stents in high-risk cases to guard against injury.

The study is not without limitations. It was retrospective, lacked a contemporaneous control group, involved only four operators across three centers, and did not employ centralized imaging review. Its results apply most directly to the kind of complex, high-risk tumors referred to specialist centers. Nevertheless, as the largest and longest-followed series of IRE for renal cancer to date, it provides the strongest real-world evidence yet that this electric-pulse technology deserves a firm place in the kidney cancer toolkit. For the growing population of patients with tumors once considered untreatable without sacrificing a kidney, the message from this nine-year, three-country experience is clear: irreversible electroporation can destroy the cancer while preserving both the organ and its function.

Subject of Research: Real-world outcomes of irreversible electroporation for complex small renal cell carcinomas unsuitable for surgery or thermal ablation

Article Title: MulticentRe rEal World outcomes of IrReversible Electroporation for complex small kiDney cancers (REWIRED)

Article References: MulticentRe rEal World outcomes of IrReversible Electroporation for complex small kiDney cancers (REWIRED). (n.d.). https://doi.org/10.1007/s44343-026-00049-z

Image Credits: AI Generated

DOI: 10.1007/s44343-026-00049-z

Keywords: irreversible electroporation, kidney cancer, renal cell carcinoma, image-guided ablation, small renal mass, NanoKnife, interventional radiology, nephron-sparing treatment, cryoablation, partial nephrectomy, RENAL nephrometry score, trifecta outcome