The research, published open access in CVIR Oncology, tackles a question that has long haunted the field: how close is too close? Tumors metastatic to the spine and pelvis frequently press against the spinal cord, the cauda equina, peripheral nerves, and visceral organs, and the thermal energy that destroys tumor cells cannot distinguish friend from foe. The magnitude of unintended injury depends on the absolute temperature achieved, the duration of the thermal dose, the temperature sensitivity of neighboring tissues, and the distance between the at-risk structure and the edge of the ablation zone. Yet despite two decades of advances, the safe distance between a lesion and a vital structure had never been firmly established, leaving clinicians to rely on intuition and case-by-case judgment.

The study team, led by Carl Stokes and colleagues at the Mallinckrodt Institute of Radiology, analyzed 100 cryoablation procedures in 91 patients and 264 RFA procedures, all performed by attending musculoskeletal radiologists with five to twenty years of experience. Roughly four in five ablations targeted metastatic lesions, with the remainder treating primary tumors. The cryoablation cohort ranged from 5 to 82 years old, while RFA patients ranged from 4 to 89, underscoring how broadly these techniques are deployed across age groups and disease states. Lesions treated with cryoablation were predominantly osseous, most often in the pelvis or chest wall, while the overwhelming majority of RFA cases, 87.1 percent, involved the spine.

The technical arsenal documented in the study reads like a catalog of modern interventional radiology. Cryoablation was performed with the Visual-ICE system using a family of cryoprobes selected for target size and location, with standard two freeze-thaw cycles and CT images acquired every two to three minutes to track the growing ice ball. Skin warming and tissue displacement using carbon dioxide gas or hydrodissection fluid, either saline, iodinated contrast, or 5 percent dextrose, were the most common protective maneuvers. In select high-stakes cases near neural structures, transcranial electrical motor evoked potentials and somatosensory evoked potentials were monitored by certified neuroelectrophysiologic technologists with more than a decade of experience each, providing a real-time electrical readout of spinal cord and nerve function during the freeze.

RFA followed a different logic. Most procedures used a bipolar probe system under fluoroscopic guidance, with built-in thermocouples tracking tissue impedance and temperature throughout ablation. In 82.8 percent of RFA cases, patient biofeedback was the sole protective mechanism, meaning an awake patient reporting sensations of heat, burning, or tingling served as the early warning system. In the remaining 17.2 percent, clinicians added active measures such as carbon dioxide dissection or hydrodissection to physically push vulnerable structures out of harm’s way. The distinction between passive protection, which monitors for impending injury, and active protection, which physically prevents it, proved central to the study’s conclusions.

The numbers tell a compelling story. Thermoprotective techniques measurably widened the safety margin in every anatomic category. For cryoablation lesions near the spinal cord or cauda equina, the mean distance increased from 1.0 centimeter to 1.3 centimeters after protection. Near peripheral nerves, the mean distance grew from 0.9 to 1.3 centimeters. The most dramatic gains appeared near visceral structures such as bowel and bladder, where the average distance of a mere 0.3 centimeters, essentially touching, was expanded to 1.3 centimeters. In the RFA cohort, lesions near the spinal canal went from a mean of 0.4 centimeters to 0.9 centimeters, and lesions adjacent to peripheral nerves more than tripled their separation, from 0.4 to 1.2 centimeters.

Complications, when they occurred, were mostly transient or self-limited. In the cryoablation group, the most common event was grade-2 transient weakness in two patients, followed by one case each of grade-3 hypertensive urgency and grade-4 hemorrhage during ablation of a chest wall hemangiopericytoma, which required emergency embolization of an intercostal artery. The single neurological event involved transient left leg weakness that resolved within 24 hours without intervention, occurring in a lesion that remained less than one centimeter from the thoracic spinal cord even after protection. In the RFA group, complications included arrhythmia, nausea, post-procedural pain requiring hospital admission, hypertensive urgency, and one venous spinal cord infarction, all in patients receiving passive protection only. Zero complications were recorded in the 44 patients who received active thermoprotection during RFA.

Two risk patterns emerged with particular clarity. First, procedural duration correlated with complications: patients who experienced adverse events averaged 217.5 minutes of cryoablation time and 137.4 minutes of RFA time, longer than cohort norms, likely reflecting case complexity. Second, the number of cryoprobes used proved a striking predictor. Complicated cases averaged 13.5 probes compared with a cohort average of 4.1, more than a threefold difference, confirming a trend previously described in the literature. Notably, concomitant cementoplasty, biopsy, and neurophysiologic monitoring added no meaningful procedure time or complication risk, and the exothermic polymerization of bone cement was insufficient to cause tumor necrosis at the bone-cement interface, corroborating earlier work.

The study’s most consequential message is a reframing of contraindications. Because no complications occurred in RFA with active protection, and only one transient deficit appeared in cryoablation even when lesions sat within a centimeter of the spinal cord, the authors argue that thermoprotection itself, rather than strict adherence to any distance threshold, is the dominant factor in mitigating risk. The clinical significance of adding a centimeter of separation remains uncertain in absolute terms, but the pattern across hundreds of cases, including 15 extremity cryoablations near the skin, a site where prior studies report skin burn rates around 2.8 percent, suggests protective techniques work. No dermal complications, infections, or superficial burns occurred in this cohort.

The authors are candid about limitations: the retrospective single-institution design, the low event rate that prevented statistically powered multivariate analysis, a single reader for image review, and the absence of recorded time spent on protective maneuvers. Still, the scale of the series, spanning more than a decade and hundreds of procedures, lends weight to its central recommendation: prophylactic use of active and passive thermoprotection whenever critical structures are at risk, and a firm rejection of proximity alone as a reason to deny patients ablation. For the growing number of patients with painful musculoskeletal tumors, many of them metastatic and with limited options, the message is that the no-go zones around the spine and nerves may be far smaller than once feared, provided the right shields are in place.

Subject of Research: Safety of thermoprotective techniques during image-guided cryoablation and radiofrequency ablation of musculoskeletal tumors

Article Title: Too close for comfort? Assessing the impact of thermoprotective techniques in image-guided ablation of musculoskeletal tumors

Article References: Stokes, C., Ly, M., Tomasian, A., Imaoka, R., Vander Velde, T. L., Northrup, B. E., Cusworth, B., & Jennings, J. W. (2025). Too close for comfort? Assessing the impact of thermoprotective techniques in image-guided ablation of musculoskeletal tumors. CVIR Oncology, 1(1), Article 18. https://doi.org/10.1007/s44343-025-00014-2

Image Credits: AI Generated

DOI: 10.1007/s44343-025-00014-2

Keywords: cryoablation, radiofrequency ablation, musculoskeletal tumors, thermoprotection, interventional radiology, spinal metastases, hydrodissection, neurophysiologic monitoring, pain palliation, interventional oncology, patient safety, image-guided ablation

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

The review synthesizes three decades of literature, spanning 1995 through early 2025, on five distinct ablation modalities applied to malignant solid tumors in patients aged 18 years or younger: radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, and electrochemotherapy. Each works through a fundamentally different biophysical mechanism. Radiofrequency ablation, the oldest and most widely studied thermal technique, drives alternating electrical current through an electrode tip, generating resistive heat that coagulates tissue at temperatures above roughly 60 degrees Celsius. Cryoablation takes the opposite approach, cycling argon and helium gases through a probe to freeze and thaw tissue, rupturing cell membranes through ice-crystal formation and osmotic stress. Microwave ablation uses electromagnetic fields at around 915 MHz or 2.45 GHz to agitate water molecules, heating tissue faster and over larger volumes than radiofrequency energy while remaining less susceptible to the heat-sink effect created by nearby blood vessels, a phenomenon in which circulating blood carries thermal energy away from the treatment zone and leaves tumor cells at the margin viable.

The two nonthermal techniques in the review sidestep heat altogether. Irreversible electroporation delivers short, high-voltage electrical pulses that destabilize cell membranes, creating permanent nanoscale pores that trigger cell death while largely preserving the protein scaffolding of surrounding tissue, including blood vessels, nerves, and ducts. That tissue-sparing property makes it theoretically attractive near critical structures such as the liver hilum, though animal work has shown that cardiac-gated synchronization is needed to prevent ventricular arrhythmias when ablation occurs near the heart. Electrochemotherapy combines intravenous or intratumoral chemotherapy, typically bleomycin, with electrical pulses that transiently permeabilize cell membranes, dramatically increasing drug uptake inside tumor cells. A 2026 case report highlighted in the review describes electrochemotherapy as a potential local treatment for residual MIBG-avid disease in refractory pediatric neuroblastoma, illustrating how the technique may reach children whose disease resists conventional therapy.

Behind the technical catalog lies an epidemiological backdrop that gives the review its urgency. The authors report that hepatoblastoma, the most common malignant liver tumor of early childhood, has shown the steepest rising incidence among ablation-relevant solid tumors, with an annual percent change of +2.17 percent. Meanwhile, five-year survival for pediatric bone tumors and soft tissue sarcomas remains stuck near 60 percent, a figure that has improved only incrementally over decades. For children with relapsed or refractory disease, options narrow sharply, and this is precisely where ablation has carved out its clinical niche. The review is emphatic on one point: surgical resection and systemic chemotherapy remain the primary treatment for all malignant solid tumors discussed, and ablation is reserved for relapsed, refractory, or surgically limited scenarios, such as pulmonary metastases of osteosarcoma that cannot all be removed surgically, or recurrent liver tumors in a child who has already undergone hepatic resection.

The clinical evidence, however, is fragile. For malignant solid tumors, the review finds the literature limited to small retrospective series with heterogeneous populations and short follow-up, precluding any conclusions about survival benefit. A phase 1 pilot study of radiofrequency ablation for recurrent pediatric solid tumors published in Cancer in 2009 remains one of the few prospective efforts, and a 2014 systematic review in Pediatric Radiology, along with a 2020 meta-analysis of interventional radiology-guided procedures in pediatric solid tumors in the European Journal of Pediatric Surgery, both concluded that the pediatric literature consists largely of case reports and single-institution experiences. A 2022 series in Pediatric Blood & Cancer on percutaneous ablation of malignant and locally aggressive solid tumors in children added valuable multi-modality data but remained retrospective. The contrast with adult interventional oncology is stark: in adults, randomized trials and large registries have established ablation as standard care for selected hepatocellular carcinomas and other lesions, while pediatric practice continues to extrapolate from devices and evidence generated for grown bodies.

That extrapolation problem is more than academic. A 2023 study in Cardiovascular and Interventional Radiology asked pointedly whether there is really no kit for kids, quantifying how few high-volume interventional radiology devices carry manufacturer recommendations for pediatric use. Ablation probes are sized, powered, and shaped for adult anatomy; a probe designed to create a five-centimeter ablation zone in an adult liver may overshoot dangerously in the liver of a toddler. Pediatric operators must therefore adapt technique on the fly, adjusting power settings, overlapping smaller ablations, and relying on experience rather than validated device labeling. The same research group published a companion analysis in 2023 on cryoablation for bone and soft tissue lesions in pediatric patients, cataloguing complications and preventive measures, and a 2024 report describing a decade of cryoablation experience in extra-abdominal desmoid tumors in children and young adults, one of the larger single-center pediatric ablation experiences in the literature.

Imaging guidance is the quiet enabler of all these techniques, and its evolution matters as much as the energy sources themselves. Ultrasound offers real-time visualization without ionizing radiation, a decisive advantage in children, but struggles with deep or bone-encased targets. Computed tomography provides precise needle-path planning for lung and bone lesions, as demonstrated in the CT-guided thermal ablation of pulmonary osteosarcoma metastases reported in Annals of Surgical Oncology in 2016. Magnetic resonance guidance represents the frontier: MR thermometry allows operators to watch temperature maps build in real time, and MR-guided focused ultrasound surgery, which ablates through intact skin without any needle at all, has established clinical services for pediatric bone tumors such as osteoid osteoma, as outlined in 2016 guidelines for building such programs. Three-dimensional visualization systems have also been paired with microwave ablation for relapsed hepatoblastoma in a small pilot study, suggesting that fusion imaging and volumetric planning will increasingly define the pediatric standard of care.

What emerges from the review is a field at an inflection point. Clinical adoption is accelerating, device technology is improving, and the biophysical rationale for each modality is well understood, yet the pediatric evidence remains confined to small, retrospective, single-institution series with heterogeneous populations and short follow-up. The authors identify a coordinated multicenter registry with standardized survival endpoints as the most urgent unmet need in the field, a call that echoes the standardization of terminology and reporting criteria established for image-guided tumor ablation in the adult literature more than a decade ago. Without shared endpoints, pooled data, and honest complication reporting, pediatric ablation risks remaining a promising anecdote rather than an evidence-based option. The review also transparently notes that generative AI was used during manuscript preparation to cross-check the literature search and copy-edit, with all content reviewed and verified by the authors, a sign of how the field’s own scholarship is modernizing.

For families facing a relapsed osteosarcoma nodule in the lung, a recurrent hepatoblastoma after resection, or a refractory neuroblastoma mass wrapped around vital structures, image-guided ablation already offers something precious: a percutaneous option that can destroy tumor while preserving tissue, function, and future growth potential. The review’s message to the medical community is that the next decade must be spent proving, not merely practicing, that promise. With hepatoblastoma incidence climbing, survival for sarcomas plateauing near 60 percent, and devices still built for adults, the children who stand to benefit most from needle-based tumor destruction are precisely those whose evidence base is weakest. Turning scattered single-center experiences into a rigorous, multicenter evidence engine, the authors argue, is no longer optional. It is the prerequisite for making image-guided ablation a standard, trusted pillar of pediatric cancer care rather than a last resort practiced in the shadows of the operating room.

Subject of Research: Image-guided percutaneous ablation modalities for malignant solid tumors in children

Article Title: Image-guided ablation for pediatric malignant solid tumors: a review of modalities, evidence, and clinical applications

Article References: Shashi, K., Sabado, J., Chewning, R., Shahin, M., & Shaikh, R. (2026). Image-guided ablation for pediatric malignant solid tumors: a review of modalities, evidence, and clinical applications. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06781-1

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06781-1

Keywords: pediatric oncology, image-guided ablation, radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, electrochemotherapy, hepatoblastoma, sarcoma, interventional radiology, Pediatric Radiology, tumor ablation