Irreversible electroporation: a novel image-guided cancer therapy

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Irreversible Electroporation (IRE) for Prostate Cancer (PCa) Treatment: The State of the Art

We evaluated the most recent research from 2000 to 2023 in order to deeply investigate the applications of PCa IRE, first exploring its usage with primary intent and then salvage intent. Finally, we discuss the differences with other focal PCa treatments. In the case of primary-intent IRE, the in-field recurrence is quite low (ranges from 0% to 33%). Urinary continence after the treatment remains high (>86%). Due to several different patients in the studies, the preserved potency varied quite a lot (59-100%). Regarding complications, the highest occurrence rates are for those of Grades I and II (20-77% and 0-29%, respectively). Grade III complications represent less than 7%. Regarding the specific oncological outcomes, both PCa-specific survival and overall survival are 100%. Metastasis-free survival is 99.6%. In a long-term study, the Kaplan-Meier FFS rates reported are 91% at 3 years, 84% at 5 years, and 69% at 8 years. In the single study with salvage-intent IRE, the in-field recurrence was 7%. Urinary continence was still high (93%), but preserved potency was significantly lower than primary-intent IRE patients (23%). In addition, Grade III complications were slightly higher (10.8%). In conclusion, in males with localized low-intermediate-risk prostate cancer, IRE had an excellent safety profile and might have positive results for sexual and urinary function.

Acute ATP loss during irreversible electroporation mediates caspase independent cell death

Irreversible electroporation (IRE) has been reported to variably cause apoptosis, necrosis, oncosis or pyroptosis. Intracellular ATP is a key substrate for apoptosis which is rapidly depleted during IRE, we sought to understand whether intracellular ATP levels is a determinant of the mode of cell death following IRE. A mouse bladder cancer cell line (MB49) was treated with electric fields while increasing the number of pulses at a fixed electric field strength, and pulse width. Cell proliferation and viability and ATP levels were measured at different timepoints post-treatment. Cell death was quantified with Annexin-V/Propidium Iodide staining. Caspase activity was measure with a fluorometric kit and western blotting. A pan-caspase (Z-VAD-FMK) inhibitor was used to assess the impact of signal inhibition. We found cell death following IRE was insensitive to caspase inhibition and was correlated with ATP loss. These findings were confirmed by cell death assays and measurement of changes in caspase expression on immunoblotting. This effect could not be rescued by ATP supplementation. Rapid and acute ATP loss during IRE interferes with caspase signaling, promoting necrosis. Cell necrosis from IRE is expected to be immunostimulatory and may be effective in cancer cells that carry mutated or defective apoptosis genes.

Irreversible electroporation for prostate cancer using PSMA PET-CT

Background

To demonstrate the clinical usefulness of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) computerized tomography (CT) for irreversible electroporation (IRE) in prostate cancer patients.

Methods

From January to May 2021, 17 men were diagnosed with localized prostate cancer through preoperative mpMRI and [¹⁸F] florastamin PSMA PET-CT imaging, followed by transperineal MRI-ultrasound fusion-guided biopsy. The patients underwent IRE focal therapy at the target lesions under general anesthesia. To evaluate the treatment outcome, serum prostate-specific antigen (PSA) levels were followed up in the 1st, 3rd, 6th, 9th, 12th months, and mpMRI was taken in the 1st and 12th months, followed by MR fusion biopsy in the 12th month post-IRE.

Results

The mean age of the patients was 66.1 ± 9.3 with a median PSA of 7.5 ng/ml. After the treatment, PSA nadir was 4.06 ± 3.4, and 11 (64.7%) achieved decline of PSA more than 50% from the baseline. Rate of negative biopsy for prostate cancer is 88% (15/17) at 12 months MR fusion biopsy after the IRE treatment. Among the relapsed cases, 1 (6.9%) patient recurred at margin of treated area, and 1 (6.9%) patient was from outfield recurrence. When excluding initial four patients, none of the patients had cancer recur.

Conclusions

When treating with IRE focal therapy, PSMA-PET CT is a potentially valuable diagnostic approach for localizing prostate cancer; it supports the detection of lesions with conventional mpMRI, enabling to perform the procedure more completely.

Pulse Parameters and Thresholds for (ir)Reversible Electroporation on Hepatocellular Carcinoma Cells in Vitro

Hepatocellular carcinoma is a leading cause of cancer-related death in many parts of the world. Traditional treatment options are not always effective. During the promising minimally invasive electroporation-based therapies, biological cell membranes are exposed to an external, sufficiently high, pulsed electric field which creates so-called nanopores into the lipid bilayer of the cell membrane. These pores can either be permanent (irreversible electroporation (IRE)), leading to apoptosis, or repairable (reversible electroporation (RE)), with continued cell function. In tumor therapy, RE is used to increase the diffusion of a chemotherapeutic drug during electrochemotherapy. For both IRE and RE, the success of the treatment is dependent on application of the appropriate electric field. Therefore, this study aims to define the pulse parameters and thresholds for IRE and RE on hepatocellular carcinoma (HepG2) cells in-vitro.In a custom-made in-vitro setup, HepG2 cell viability (0, 5, 10, and 15 min), and the peak temperature were measured after electroporation with the different IRE and RE pulsing protocols, to determine the most successful settings for IRE and RE. A CAM/PI flow cytometric assay was performed to confirm cell permeabilization for the RE pulsing protocols with the highest cell viability.The results indicated that an IRE pulsing protocol (70 pulses, 100 µs pulse length, and 100 ms interval) with an electric field strength of 4000 V/cm was needed as threshold for almost complete cell death of HepG2 cells. A RE pulsing protocol (8 pulses, 100 µs pulse length, and 1000 ms interval) with an electric field strength of 1000 V/cm was needed as threshold for viable and permeabilized HepG2 cells. The low peak temperatures (max 30.1°C for IRE, max 23.1°C for RE) within this study indicated that the reduction in HepG2 cell viability was caused by the applied electric field and was not a result of Joule heating.

Liver tissue remodeling following ablation with irreversible electroporation in a porcine model

Irreversible electroporation (IRE) is a method of non-thermal focal tissue ablation characterized by irreversibly permeabilizing the cell membranes while preserving the extracellular matrix. This study aimed to investigate tissue remodeling after IRE in a porcine model, especially focusing on the extracellular matrix and hepatic stellate cells. IRE ablation was performed on 11 female pigs at 2,000 V/cm electric field strength using a versatile high-voltage generator and 3 cm diameter parallel-plate electrodes. The treated lobes were removed during surgery at 1, 3, 7, 14, and 21 days after IRE. Tissue remodeling and regeneration were assessed by histopathology and immunohistochemistry. Throughout the treated area, IRE led to extensive necrosis with intact collagenous structures evident until day 1. From then on, the necrosis progressively diminished while reparative tissue gradually increased. During this process, the reticulin framework and the septal fibrillar collagen remained in the necrotic foci until they were invaded by the reparative tissue. The reparative tissue was characterized by a massive proliferation of myofibroblast-like cells accompanied by a complete disorganization of the extracellular matrix with the disappearance of hepatic architecture. Hepatic stellate cell markers were associated with the proliferation of myofibroblast-like cells and the reorganization of the extracellular matrix. Between 2 and 3 weeks after IRE, the lobular architecture was almost completely regenerated. The events described in the present study show that IRE may be a valid model to study the mechanisms underlying liver regeneration after extensive acute injury.

Differential effect of high-frequency electroporation on myocardium vs. non-myocardial tissues

AIMS

Pulsed-field ablation (PFA) is an emerging non-thermal ablation method based on the biophysical phenomenon of electroporation. Data on PFA cardiac selectivity nature and tissue-specific thresholds are lacking. We aim to compare the in vivo differential effect of high-frequency irreversible electroporation (HF-IRE) protocols on various tissues.

METHODS AND RESULTS

Twenty-three Sprague-Dawle rodents were allocated into three different protocols of 300, 600, and 900 V, respectively, while delivering twenty 100 µs bursts of a 150 kHz biphasic square wave to five tissues; cardiac muscle, skeletal muscle, liver, carotid artery and sciatic nerve. Lesions were evaluated quantitatively by histologic analysis and by morphometric evaluation. There were eight, seven and eight animals in the 300, 600, and 900 V protocols, respectively. High-frequency electroporation protocols showed a graded effect on myocardial tissue with larger lesions in the 900 V protocol compared with the other two protocols as demonstrated by width (P = 0.02), length (P = 0.01) and fibrosis ratio (P = 0.001). This effect was not observed for other tissues with attenuated degree of damage. No damage to the carotid artery was observed in all protocols. Partial damage to the sciatic nerve was observed in only two samples (25%) in the 600 V group and in one sample (14.3%) in the 900 V group.

CONCLUSION

Electroporation effect is tissue-specific such that myocardium is more prone to electroporation damage compared with neural and vascular tissues. Our results suggest no neural or vascular damage with using a low-amplitude HF-IRE protocol. Further investigation is warranted to better identify other tissue-specific thresholds.

Novel irreversible electroporation ablation (Nano-knife) versus radiofrequency ablation for the treatment of solid liver tumors: a comparative, randomized, multicenter clinical study

Irreversible electroporation (IRE) is a soft tissue ablation technique that uses short electrical fields which induce the death of target cells. To evaluate the safety and efficacy of an IRE-based device compared to regular radiofrequency ablation (RFA) of solid liver tumors, in this multicenter, randomized, parallel-arm, non-inferiority study, 152 patients with malignant liver tumors were randomized into IRE (n = 78) and RFA (n = 74) groups. The primary endpoint was the success rate of tumor ablation; the secondary endpoints included the tumor ablation time, complications, tumor recurrence rates and treatment-related adverse events (TRAE). The success rate of tumor ablation using IRE was 94.9% and was non-inferior to the RFA group (96.0%) (P = 0.761). For the secondary endpoints, the average ablation time was 34.29 ± 30.38 min for the IRE group, which was significantly longer than for the RFA group (19.91 ± 16.08 min) (P < 0.001). The incidences of postoperative complications after 1 week (P = 1.000), 1 month (P = 0.610) and 3 months (P = 0.490) were not significantly different between the 2 groups. The recurrence rates of liver tumor at 1, 3 and 6 months after ablation were 0 (0.0%), 10 (13.9%) and 10 (13.3%) in the IRE group and 2.9%, 7.3% and 19.7% in the RFA control group (all P > 0.05), respectively. For safety assessments, 51 patients experienced 191 AEs (65.4%) in the IRE group, which was not different from the RFA group (73.0%, 54/184) (P = 0.646). In 7 IRE patients, 8 TRAEs (7.9%) occurred, the most common being edema of the limbs (mild grade) and fever (severe grade), while no TRAEs occurred in the RFA group. This study proved that the excellent safety and efficacy of IRE was non-inferior to the regular radiofrequency device in ablation performance for the treatment of solid liver tumors. Clinical trial registration: Chinese Clinical Trial Registry: ChiCTR1800017516

Irreversible Electroporation for Hepatocellular Carcinoma Abutting the Diaphragm: A Prospective Single-center Study

BACKGROUND AND AIMS

Irreversible electroporation (IRE) is an emerging local ablation therapy which may be effective for unresectable tumors. This study aimed to evaluate the safety and efficacy of percutaneous IRE in the treatment of hepatocellular carcinoma (HCC) abutting the diaphragm.

METHODS

A total of 26 participants with 39 tumors abutting the diaphragm were prospectively evaluated between July 2015 and September 2018. Complications associated with IRE were recorded, and the survival benefit of IRE was analyzed. The factors associated with time to local tumor progression (LTP) were analyzed using univariate and multivariate Cox regression models.

RESULTS

No major complications or treatment-related deaths occurred. The technical success rate was 96.2% (25/26) and complete ablation rate was 92.3% (36/39). The median follow-up period was 16.7 months (range: 3.0-43.0 months), the LTP occurred in 15.2% of tumors and median time to LTP was 20.4 months. Overall, tumor size (hazard ratio: 1.24 [95% confidence interval: 0.38, 3.81], p=0.03) was the only factor associated with time to LTP.

CONCLUSIONS

This study shows for the first time that percutaneous IRE is a safe and effective ablation technology for HCC abutting the diaphragm.

Neutrophils direct preexisting matrix to initiate repair in damaged tissues

Internal organs heal injuries with new connective tissue, but the cellular and molecular events of this process remain obscure. By tagging extracellular matrix around the mesothelium lining in mouse peritoneum, liver and cecum, here we show that preexisting matrix was transferred across organs into wounds in various injury models. Using proteomics, genetic lineage-tracing and selective injury in juxtaposed organs, we found that the tissue of origin for the transferred matrix likely dictated the scarring or regeneration of the healing tissue. Single-cell RNA sequencing and genetic and chemical screens indicated that the preexisting matrix was transferred by neutrophils dependent on the HSF-integrin AM/B2-kindlin3 cascade. Pharmacologic inhibition of this axis prevented matrix transfer and the formation of peritoneal adhesions. Matrix transfer was thus an early event of wound repair and provides a therapeutic window to dampen scaring across a range of conditions.

Irreversible electroporation in renal tumours: A systematic review of safety and early oncological outcomes

We review the safety and early oncological outcomes of irreversible electroporation (IRE), a novel non-thermal ablation technique, in small renal masses (SRMs). Following PROSPERO registration (CRD42020197943), a systematic search of MEDLINE, EMBASE and SCOPUS databases according to PRISMA guidelines was performed. Critical appraisal of the included studies was performed using the Newcastle-Ottawa Scale. Of 224 articles screened, 10 met the inclusion criteria. In total, 83 patients were identified. Except for one cohort study (n = 41), the remaining studies were case series of n < 10. Follow up was <12 months in 7/10 articles (range 3–34 months). About 10/10 articles reported safety outcomes. There were no 30-day mortalities. The most frequently reported adverse events were transient haematuria (11/83) and asymptomatic perirenal haematomas (7/83). About 62/63 patients with reported length of stay were discharged within 24 h. No significant long-term changes in renal function were reported. About 7/10 articles reported oncological outcomes. Only one article assessed histopathological outcomes, whilst the remaining studies used cross-sectional imaging modalities to assess efficacy, recurrence or disease progression. About 4/7 patients with histopathology outcomes, showed complete response (CR). About 43/55 patients with radiological outcomes showed CR. No mortalities were reported due to SRMs. These initial findings support IRE as safe and feasible in managing SRMs. However, results from larger studies with longer follow-up are needed to evaluate oncological outcomes and compare these with other ablation methods.

Local Treatments in the Unresectable Patient with Colorectal Cancer Metastasis: A Review from the Point of View of the Medical Oncologist

For patients with isolated liver metastases from colorectal cancer who are not candidates for potentially curative resections, non-surgical local treatments may be useful. Non-surgical local treatments are classified according to how the treatment is administered. Local treatments are applied directly on hepatic parenchyma, such as radiofrequency, microwave hyperthermia and cryotherapy. Locoregional therapies are delivered through the hepatic artery, such as chemoinfusion, chemoembolization or selective internal radiation with Yttrium 90 radioembolization. The purpose of this review is to describe the different interventional therapies that are available for these patients in routine clinical practice, the most important clinical trials that have tried to demonstrate the effectiveness of each therapy and recommendations from principal medical oncologic societies.

Focal therapy for primary and salvage prostate cancer treatment: a narrative review

Despite innovations in surgical technology and advancements in radiation therapy, radical treatments for clinically localized prostate cancer are associated with significant patient morbidity, including both urinary and sexual dysfunction. This has created a vital need for therapies and management strategies that provide an acceptable degree of oncologic efficacy while mitigating these undesirable side effects. Successful developments in screening approaches and advances in prostate imaging have allowed clinicians to identify, localize, and more precisely target early cancers. This has afforded urologists with an important opportunity to develop and employ focal ablation techniques that selectively destroy tumors while preserving the remainder of the gland, thus avoiding detrimental treatment effects to surrounding sensitive structures. A lack of high-level evidence supporting such an approach had previously hindered widespread adoption of focal treatments, but there are now numerous published clinical trials which have sought to establish benchmarks for safety and efficacy. As the clinical evidence supporting a potential role in prostate cancer treatment begins to accumulate, there has been a growing acceptance of focal therapy in the urologic oncology community. In this narrative review article, we describe the techniques, advantages, and side effect profiles of the most commonly utilized focal ablative techniques and analyze published clinical trial data supporting their evolving role in the prostate cancer treatment paradigm.

Clinical Applications and Immunological Aspects of Electroporation-Based Therapies

Reversible electropermeabilization (RE) is an ultrastructural phenomenon that transiently increases the permeability of the cell membrane upon application of electrical pulses. The technique was described in 1972 by Neumann and Rosenheck and is currently used in a variety of applications, from medicine to food processing. In oncology, RE is applied for the intracellular transport of chemotherapeutic drugs as well as the delivery of genetic material in gene therapies and vaccinations. This review summarizes the physical changes of the membrane, the particularities of bleomycin, and the immunological aspects involved in electrochemotherapy and gene electrotransfer, two important EP-based cancer therapies in human and veterinary oncology.

Margin Accentuation Irreversible Electroporation in Stage III Pancreatic Cancer: A Systematic Review

Simple Summary

This literature review shows preliminary evidence to suggest that electroporation, the use of electricity to cause the death of cells around the tumour, may be associated with an improved survival and complete resection rates following pancreatic surgery for higher stage pancreatic cancer. However, one in five patients have a complication from the procedure that alters their normal course in hospital. Moreover, the number of patients who underwent this technique is small and further data is needed to support the preliminary evidence. The results therefore should be interpreted with caution.

Abstract

The present systematic review aimed to summarise the available evidence on indications and oncological outcomes after MA IRE for stage III pancreatic cancer (PC). A literature search was performed in the Pubmed, MEDLINE, EMBASE, SCOPUS databases using the PRISMA framework to identify all MA IRE studies. Nine studies with 235 locally advanced (LA) (82%, 192/235) or Borderline resectable (BR) PC (18%, 43/235) patients undergoing MA IRE pancreatic resection were included. Patients were mostly male (56%) with a weighted-mean age of 61 years (95% CI: 58–64). Pancreatoduodenectomy was performed in 51% (120/235) and distal pancreatectomy in 49% (115/235). R0 resection rate was 73% (77/105). Clavien Dindo grade 3–5 postoperative complications occurred in 19% (36/187). Follow-up intervals ranged from 3 to 29 months. Local and systematic recurrences were noted in 8 and 43 patients, respectively. The weighted-mean progression free survival was 11 months (95% CI: 7–15). The weighted-mean overall survival was 22 months (95% CI 20–23 months) and 8 months (95% CI 1–32 months) for MA IRE and IRE alone, respectively. Early non-randomised data suggest MA IRE during pancreatic surgery for stage III pancreatic cancer may result in increased R0 resection rates and improved OS with acceptable postoperative morbidity. Further, larger studies are warranted to corroborate this evidence.

3D mixed-reality visualization of medical imaging data as a supporting tool for innovative, minimally invasive surgery for gastrointestinal tumors and systemic treatment as a new path in personalized treatment of advanced cancer diseases

Background

The purpose of this study was to investigate the potential of a combination of 3D mixed-reality visualization of medical images using CarnaLife Holo (MedApp, Poland) system as a supporting tool for innovative, minimally invasive surgery/irreversible electroporation—IRA, Nano-Knife), microwave ablation (MWA)/for advanced gastrointestinal tumors. Eight liver and pancreatic tumor treatments were performed. In all of the patients undergoing laparoscopy or open surgery volume and margin were estimated by preoperative visualization. In all patients, neoplastic lesions were considered unresectable by standard methods.

Methods

Preoperative CT or MRI were transformed into holograms and displayed thanks to the HoloLens 2. During operation, the surgeon’s field of view was augmented with a 3D model of the patient’s relevant structures.

Results

The intraoperative hologram contributed to better presentation of tumor size and locations, more precise setting of needles used to irreversible electroporation and for determining ablation line in case of liver metastases. Surgeons could easily compare the real patient's anatomy to holographic visualization just before the operations.

Conclusions

The combination of 3D mixed-reality visualization using CarnaLife Holo with IRA, MWA and next systemic treatment (chemotherapy) might be a new way in personalized treatment of advanced cancers.

Irreversible Electroporation of Recurrent Hepatocellular Carcinoma After Liver Transplantation: Report of Two Cases

The treatment strategies of post-transplant hepatocellular carcinoma (HCC) recurrence have not been completely clarified. Thermal ablative techniques have been increasingly performed for the treatment of post-transplant HCC recurrences. However, thermal ablation can create abnormal communication with the biliary tract and the ablation site by causing biliary injury. This abnormal communication may cause bacterial contamination and abscess formation. Irreversible electroporation (IRE) is a nonthermal ablative technique which may reduce the risk of abscess development at the ablation site due to its low risk of thermal injury to the biliary system. IRE may also preserve the perilesional blood vessels. This report describes two cases of post-transplant intrahepatic HCC recurrence which were successfully treated with IRE.

Initial experience of irreversible electroporation for locally advanced pancreatic cancer in a Korean population

BACKGROUND

Locally advanced pancreatic cancer (LAPC) is one of the most aggressive malignancies. Irreversible electroporation (IRE) is a novel technique that uses a non-thermal ablation to avoid vessel or duct injury.

PURPOSE

To investigate the safety and efficacy of IRE for the management of LAPC in a Korean population.

MATERIAL AND METHODS

Twelve patients (median age 64 years; age range 46-73 years) treated between December 2015 and March 2017 underwent intraoperative IRE for LAPC. Technical success and clinical outcomes, including complications, serum pancreatic enzyme levels, overall survival (OS), and progression-free survival (PFS), were evaluated.

RESULTS

Tumors were located in the pancreas head in 7 (58.3%) patients and in the body/tail in 5 (41.7%) patients. The median tumor diameter in the longest axis was 3.1 cm. Vascular invasion was observed in all patients and bowel abutment in 3 (25%) patients. Technical success was achieved in all patients. The median serum levels of amylase and lipase were 55 U/L and 31 U/L, respectively, at baseline, increased to 141.5 U/L (P = 0.008) and 53 U/L (P = 0.505), respectively, one day after IRE, and normalized after one week. The rate of 30-day mortality of unknown relation was 8.3% (one individual experienced massive hematemesis 12 days after IRE). The median OS from diagnosis and IRE was 24.5 months and 13.5 months, respectively. The median PFS from diagnosis and IRE was 19.2 months and 8.6 months, respectively.

CONCLUSION

For patients with LAPC, IRE appears to be a promising treatment modality with an acceptable safety profile.

Intratumoral STING Agonist Injection Combined with Irreversible Electroporation Delays Tumor Growth in a Model of Hepatocarcinoma

BACKGROUND/AIM

Irreversible electroporation (IRE) showed promising results for small-size tumors and very early cancers. However, further development is needed to evolve this procedure into a more efficient ablation technique for long-term control of tumor growth. In this work, we show that it is possible to increase the antitumor efficiency of IRE by simmultaneously injecting c-di-GMP, a STING agonist, intratumorally.

MATERIALS AND METHODS

Intratumoral administration of c-di-GMP simultaneously to IRE was evaluated in murine models of melanona (B16.OVA) and hepatocellular carcinoma (PM299L).

RESULTS

The combined therapy increased the number of tumor-infiltrating IFN-γ/TNF-α-producing CD4 and CD8 T cells and delayed tumor growth, as compared to the effect observed in groups treated with c-di-GMP or IRE alone.

CONCLUSION

These results can lead to the development of a new therapeutic strategy for the treatment of cancer patients refractory to other therapies.

Irreversible electroporation in patients with liver tumours: treated-area patterns with contrast-enhanced ultrasound

BACKGROUND

Familiarity with post-IRE imaging interpretation is of considerable importance in determining ablation success and detecting recurrence. CEUS can be used to assess the tumour response and characteristics of the ablation zone. It is of clinical interest to describe the ultrasonographic findings of liver tumours after irreversible electroporation (IRE) percutaneous ablation.

METHODS

A prospective study of 24 cases of malignant liver tumours (22 cases of primary liver tumours and 2 cases of liver metastases) treated by IRE ablation was conducted. Two inspectors evaluated the ablation zone in a consensus reading performed immediately, 1 day, and 1 month after IRE ablation. The gold standard method, magnetic resonance imaging (MRI), was used to evaluate the effectiveness of the treatment at 1 month.

RESULTS

Immediately after IRE ablation and up to 1 month later, the ablation zones gradually changed from hypo-echogenicity to hyper-echogenicity on conventional ultrasound and showed non-enhancement on contrast-enhanced ultrasound (CEUS). One month after IRE ablation, CEUS and MRI results were highly consistent (κ = 0.78, p < 0.05).

CONCLUSIONS

We conclude that CEUS may be an effective tool for assessing post-IRE ablation changes after 1 month. CEUS enables the depiction of tumour vascularity in real time and serves as an easy, repeatable method.

Predictors of Occlusion of Hepatic Blood Vessels after Irreversible Electroporation of Liver Tumors

PURPOSE

To examine predictors of midterm occlusion in portal and hepatic veins within or adjacent to the ablation zone after irreversible electroporation (IRE) of liver tumors.

MATERIALS AND METHODS

This retrospective cohort analysis included 39 patients who underwent CT-guided IRE of liver tumors. Vessels within or adjacent to the ablation zone were identified on CT images acquired immediately after the procedure, and the positional relationships with the ablation zone (within/adjacent), locations (proximal/distal), and diameters (< 4 mm or ≥ 4 mm) were evaluated. Using contrast-enhanced follow-up scans, each vessel was classified as patent, stenosed, or occluded. Associations between vessel occlusion and each variable were investigated.

RESULTS

Overall, 33 portal veins and 64 hepatic veins were analyzed. Follow-up scans showed occlusion in 12/33 (36.7%) portal veins and 17/64 (26.6%) hepatic veins. Vessels within the ablation zone were occluded significantly more frequently than vessels adjacent to the ablation zone (portal: 55.6% [10/18] vs 13.3% [2/15], P = .04; hepatic: 45.4% [15/33] vs 6.4% [2/31], P = .011). Vessels with a diameter < 4 mm were also occluded significantly more frequently than vessels with a diameter ≥ 4 mm (portal: 72.7% [8/11] vs 18.1% [4/22], P = .011; hepatic: 54.8% [17/31] vs 0% [0/33], P < .001). The respective positive and negative predictive values for occlusion of vessels categorized as both within and < 4 mm were 88% (7/8) and 82% (20/25) for portal veins and 79% (15/19) and 96% (43/45) for hepatic veins.

CONCLUSIONS

Midterm vessel occlusion after liver IRE could be predicted with relatively high accuracy by assessing ablation location and vessel diameter.

Irreversible Electroporation For Hepatocellular Carcinoma: Longer-Term Outcomes At A Single Centre

BACKGROUND AND AIMS

Irreversible electroporation (IRE) is a non-thermal ablation technique for unresectable hepatocellular carcinoma (HCC) not amenable to standard thermal ablation. The aim of this study was to report our longer-term outcomes using this treatment modality.

METHOD

We identified all patients at our institution who underwent IRE for HCC between December 2008 and October 2019 as recommended after multi-disciplinary team review. Demographic, clinical, tumour response and survival data up until 1 March, 2020 were analysed. The primary outcome was local recurrence-free survival (LRFS) in patients who had a complete response (CR). Secondary outcomes included CR rates, procedure-related complications and the incidence of death or liver transplantation.

RESULTS

A total of 23 patients (78% males, median age 65.2 years) received IRE therapy to 33 HCC lesions during the study period with the median tumour size being 2.0 cm (range 1.0-5.0 cm). Twenty-nine (87.9%) lesions were successfully ablated after one (n = 26) or two (n = 3) procedures. The median follow-up time for these lesions was 20.4 months. The median overall LRFS was 34.5 (95% CI 24.8 -) months with a 6- and 12-month LRFS of 87.9% (95% CI 75.8-100) and 83.6% (95% CI 70.2-99.7), respectively. Tumours < 2 cm had a 12-month LRFS of 100% (95% CI 100-100).

CONCLUSION

IRE appears to be an efficacious local ablative method for early stage HCC not amenable to standard ablative techniques, with very good CR rates and longer-term LRFS, particularly for smaller lesions. Further studies comparing this technique to more widely accepted ablative methods such as radiofrequency and microwave ablation are warranted.

Effects of irreversible electroporation on femoral nerves in a rabbit model

INTRODUCTION

Irreversible electroporation (IRE) is a novel technique that uses a non-thermal ablation to avoid adjacent major structure injury. The aim of this study was to sequentially evaluate the effects of IRE on the femoral nerve during acute-to-delayed periods in a rabbit model.

MATERIAL AND METHODS

Ultrasound-guided IRE of femoral neurovascular bundles was performed in seven rabbits. Functional and histopathologic evaluation was performed sequentially after IRE. The extent of nerve fiber affected, and the proportion of perineurial inflammation and surrounding tissue injury were recorded.

RESULTS

After IRE, femoral nerve function was damaged before four weeks, but then gradually returned to normal. Perineural inflammatory cell infiltration was most severe three days after IRE (80-85%), and was normalized after eight weeks. Surrounding tissue injury was prominent at three days and one week after IRE (80-90%), and then gradually recovered. However, peripheral nerve fibers were markedly damaged at one and two weeks (80-100%). Nerve fibers then recovered and were normalized at eight weeks.

CONCLUSION

Nerve tissue injury with transient functional impairment can occur after IRE. However, endoneurial and epineurial extracellular matrix were preserved with Schwann cell regeneration, which could lead to regeneration of nerve tissues within eight weeks.

Clinical impact of irreversible electroporation ablation for unresectable hilar cholangiocarcinoma

Irreversible electroporation (IRE) is a non-thermal ablation modality that has been shown to be safe and effective in its application to tumors that are close to risky areas. This study aims to assess the safety and efficacy of IRE for unresectable hilar cholangiocarcinoma. Nine patients from two medical centers in Asia received IRE treatment between June 2015 and July 2017. Before IRE treatment, percutaneous biliary decompressions had been performed on eight patients, and internal stenting had been performed on one patient. All patients tolerated the procedure well without high-grade complications. The ablated tumors had constant size without contrast enhancement for more than three months in eight patients and the level of CA19-9 decreased significantly in all patients. The percutaneous biliary drainage tube was removed from two patients with recanalization of the bile duct. The internal stent in one patient was removed without further stenting. The median overall survival period was 26 months, and the progression-free survival was 18 months. Bile ducts remained narrow in the majority (2/3) of the treated patients. Nevertheless, IRE ablation of unresectable hilar cholangiocarcinoma involving vital structures is a safe and feasible primary treatment for local tumor control and is effective in prolonging survival.

Design of a High Voltage Pulse Generator with Large Width Adjusting Range for Tumor Treatment

The unique biological effects stimulated by short pulsed electric field have many applications in tumor treatment, such as irreversible electroporation, electrochemotherapy, gene transfection and immune therapy. These biological effects require high voltage pulses with different pulse width in the range from nanoseconds to hundreds of microseconds. To fulfill this requirement, a compact high voltage pulse generator has been designed based on a switchable capacitor array and a SiC MOSFET switching array. The proposed pulse generator has one output channel with an adjustable pulse width from 100 ns to 100 µs, an amplitude range from 0 kV to 2 kV, a repetition rate less than 1.2 kHz and a voltage drop less than 5%. The mechanism of the stacked switches circuit was investigated, in connection with a switchable capacitor array. The introduction of a switchable capacitor array extends the pulse width from nanosecond scale and microsecond scale compared with other similar design methods. The pulse generator has been designed in simulation and implemented in experiment. The developed pulse generator provides a convenient and economical tool for the further studies of the unique biological effects stimulated by different pulsed electric fields for tumor treatment.

Thermodynamic profiling during irreversible electroporation in porcine liver and pancreas: a case study series

AIMS

First, the aim of the study was to determine whether irreversible electroporation (IRE) is associated with heat generation in the liver and pancreas at clinical (≤1,500 V/cm) and supraclinical (>1,500 V/cm) electroporation settings; second, to assess the risk of thermal tissue damage in and adjacent to the treated volume in highly perfused versus moderately perfused parts of both organs; third, to investigate the influence of perfusion and of the presence and the orientation of a metal stent on the maximal thermal elevation (ΔT_Session,max) in the tissue during an IRE session at fixed IRE settings, and finally, to determine whether the maximum temperature elevation within the IRE-subjected organ during an IRE treatment (single or multiple sessions) is reflected in the organ's surface temperature.

METHODS

The aims were investigated in 12 case studies conducted in five female Landrace pigs. Several IRE settings were applied for lateral (2), triangular (3), and rectangular (4) electrode configurations in the liver hilum, liver periphery, pancreas head, and pancreas tail. IRE series of 10-90 pulses were applied with pulse durations that varied from 70 μs to 90 μs and electric field strengths between 1,200 V/cm and 3,000 V/cm. In select cases, a metal stent was positioned in the bile duct at the level of the liver hilum. Temperatures were measured before, during, and after IRE in and adjacent to the treatment volumes using fiber optical temperature probes (temperature at the nucleation centers) and digital thermography (surface temperature). The occurrence of thermal damage was assumed to be at temperatures above 50 °C (ΔT_Session,max ≥ 13 °C relative to body temperature of 37 °C). The temperature fluctuations at the organ surface (ΔT_LocSurf) were compared to the maximum temperature elevation during an IRE treatment in the electroporation zone. In select cases, IRE was applied to tissue volumes encompassing the portal vein (PV) and a constricted and patent superior mesenteric vein (SMV) to determine the influence of the heatsink effect of PV and SMV on ΔT_Session,max.

RESULTS

The median baseline temperature was 31.6 °C-36.3 °C. ΔT_Session,max ranged from -1.7 °C to 25.5 °C in moderately perfused parts of the liver and pancreas, and from 0.0 °C to 5.8 °C in highly perfused parts. The median ΔT_LocSurf of the liver and pancreas was 1.0 °C and 10.3 °C, respectively. Constricting the SMV in the pancreas head yielded a 0.8 °C higher ΔT_Session,max. The presence of a metal stent in the liver hilum resulted in a ΔT_Session,max of 19.8 °C. Stents parallel to the electrodes caused a ΔT_Session,max difference of 4.2 °C relative to the perpendicular orientation.

CONCLUSIONS

Depending on IRE settings and tissue type, IRE is capable of inducing considerable heating in the liver and pancreas that is sufficient to cause thermal tissue damage. More significant temperature elevations are positively correlated with increasing number of electrode pairs, electric field strength, and pulse number. Temperature elevations can be further exacerbated by the presence and orientation of metal stents. Temperature elevations at the nucleation centers are not always reflected in the organ's surface temperature. Heat sink effects caused by large vessels were minimal in some instances, possibly due to reduced blood flow caused by anesthesia.

RELEVANCE FOR PATIENTS

Appropriate IRE settings must be chosen based on the tissue type and the presence of stents to avoid thermal damage in healthy peritumoral tissue and to protect anatomical structures [Table: see text].

Prevention of Procedural Hypertension in the Irreversible Electroporation Ablation of Liver and Pancreatic Tumors Based on Distance from the Adrenal Gland

Background and objective

When irreversible electroporation (IRE) ablation of abdominal tumors, procedural hypertension often occurs, which often affects the progress of the ablation. Until now, there is no reasonable explanation for this phenomenon. The objective of this research was to explore the cause and solution of procedural hypertension in percutaneous IRE.

Methods

In this study, the treatment data of 4 consecutive groups of patients were used to confirm the cause of intraoperative hypertension and then verify the solution. A total of 155 patients with procedural hypertension were screened based on their medical records of pancreatic or hepatic IRE treatment. Procedural hypertension was monitored in 21 new patients, the correlation between serum catecholamines and hypertension was recorded and evaluated using regression analysis. Forty new patients were divided into two groups (distance from needle tip to adrenal gland, < 2 cm vs ≥ 2 cm), and the blood pressure was recorded and compared with two-way ANOVA. Eleven patients with ablative distance <2 cm were treated in advance with phentolamine to observe for the occurrence of procedural hypertension.

Results

Of the 21 re-enrolled patients with ablation of the pancreas and liver tumors, 9 developed intraoperative hypertension with significantly elevated serum catecholamines levels, epinephrine, norepinephrine and dopamine are all positively associated with hypertension, with P values were 0.0003, 0.0253, and 0.0015, respectively. For the two groups with different needle-insertion distances, hypertension in the < 2 cm group was more significant than that in the other group (for procedural hypertension, P< 0.01; for heart rate, P< 0.05), which was considered as a high-risk group. The occurrence of intraoperative hypertension could be completely prevented by using phentolamine prior to treatment.

Conclusion

Hypertension occurs frequently during hepatic and pancreatic IRE because of the damage of adrenal gland. The safe distance of ablation probe for the adrenal gland was 2 cm. For high-risk patients, early drug prevention works well.

The interaction between irreversible electroporation therapy (IRE) and embolization material using a validated vegetal model: an experimental study

PURPOSE

Irreversible electroporation (IRE) is a nonthermal tumor ablation technique that induces cell apoptosis while preserving extracellular architecture. Surgical clips and embolic agents may lie adjacent to, or within, the target lesion. It is unknown to date if IRE causes degradation to the embolic agents or surgical clips that may have adverse effects to patients. We aimed to examine the effects of the IRE on the morphology of various embolic agents and the effects of these agents to the ablation field using a previously validated vegetal model.

METHODS

Metallic surgical clips and various metallic and nonmetallic embolic agents were inserted within the center of the tuber ablation field. Additionally, clips were inserted on the edge and outside the ablation field. One tuber was ablated as a control. Ablation settings were based on previous published experiments. Tubers were imaged with magnetic resonance imaging (MRI) 18-24 hours after ablation and the ablated field dimensions were measured. Nonmetallic embolic agents were examined microscopically by the pathologist.

RESULTS

Nonmetallic agents did not affect the ablation pattern. Metallic implants, however, caused arcing of the ablation margins. There was no macroscopic or microscopic degradation to the agents after IRE.

CONCLUSION

The ablation zone arced in the presence of surgical clips at the edge or outside the ablation margins; therefore, nearby critical structures may be susceptible to the effects of IRE. Furthermore, there was no physical degradation of the embolic agents or surgical clips, and this may have importance when considering IRE ablation of previously embolized lesions in vivo.

Ablative, Endovascular, and Biliary Interventions for Patients with Pancreatic Cancer

Interventional radiologists have multiple points of involvement in the treatment and management of patients with pancreatic adenocarcinoma. There is increasing interest in cytoreductive treatment of the primary tumor as well as metastatic disease via arterial and ablative techniques. The focus of this article is on the current evidence for pancreatic irreversible electroporation. For patients undergoing curative surgery or terminal palliation, interventional radiology can manage complications and symptoms. In this article, therapeutic and palliative options in this group of patients including postoperative embolization, biliary drainage, and stent placement are reviewed.

[Ablative therapy of small renal masses]

Renal cell cancer is nowadays predominantly diagnosed in early stages due to the widespread use of sectional imaging for unrelated symptoms. Small renal masses (<4 cm) feature a largely indolent biology with a very low risk for metastasis or even a benign biology in up to 30% of the cases. Consequently, there is a need for less invasive therapeutic alternatives to nephron-sparing surgery. Meanwhile, there is a broad portfolio of local ablation techniques to treat small renal tumors. These include the extensively studied radiofrequency ablation and cryoablation techniques as well as newer modalities like microwave ablation and irreversible electroporation as more experimental techniques. Tumor ablation can be performed percutaneously under image guidance or laparoscopically. In particular, the percutaneous approach is a less invasive alternative to nephron-sparing surgery with lower risk for complications. Comparative studies and meta-analyses report a higher risk for local recurrence after renal tumor ablation compared to surgery. However, long-term oncological results after treatment of small renal masses are promising and do not seem to differ from partial nephrectomy. The possibility for salvage therapy in case of recurrence also accounts for this finding. Especially old patients with an increased risk of surgical and anesthesiological complications as well as patients with recurrent and multiple hereditary renal cell carcinomas may benefit from tumor ablation. Tumor biopsy prior to intervention is associated with very low morbidity rates and is oncologically safe. It can help to assess the biology of the renal mass and prevent therapy of benign lesions.

Irreversible electroporation ablation of end-stage metastatic retroperitoneal lesions: Report on three cases and literature review

Metastatic retroperitoneal tumors constitute an end-stage disease with poor prognosis that represents a heavy global health burden. The present study aimed to explore the efficacy of irreversible electroporation ablation (IRE) therapy in patients with end-stage retroperitoneal tumors. Between April 2016 and September 2017, three patients with unresectable retroperitoneal malignant tumors were enrolled. Among these cases, ultrasound (US)-guided IRE was palliatively performed for targeting 3 tumors (1 tumor per patient) located around the abdominal aorta. Post-treatment contrast-enhanced US (CEUS) and contrast-enhanced computed tomography (CECT) scans were subsequently performed to evaluate the area adjacent to the ablation zone and determine the prognosis. During the follow-up, the cases experienced a reduction of pain (mean score of 5.8 decreased to 2.2, based on the visual analogue scale), and had an overall survival rate ranging from 2 to 11 months. Case 1 remained alive at the time of submission of this study, but case 2 died within 2 months and case 3 within 11 months due to liver metastases of the primary tumor. At the 3-week follow-up, the CEUS image for case 1 exhibited a contrast defect with a sufficient ablation margin, in accordance with the CECT at 1.5 months following IRE, exhibiting complete tumor necrosis without contrast enhancement. Overall, these results suggest that US-guided percutaneous IRE may be effective in the treatment of end-stage retroperitoneal tumors. However, further studies are required to substantiate the conclusions of the present study. The present clinical trial was registered at clinicaltrials.gov (ID: NCT02822066) on June 20th, 2016.

Characterization of irreversible electroporation on the stomach: A feasibility study in rats

Irreversible electroporation (IRE) is a newly developed non-thermal ablative therapy. During the IRE procedure, the permeability of the cell membrane is irreversibly changed by application of high-energy pulses across the tissue. This induces the breakdown of cell homeostasis, and thereby cell death. Here, we present an in vivo study to demonstrate IRE ablation of gastric tissue and characterize the changes that occur with time therein. No significant complications were observed in the test rats during the experiment. The electroporated tissues exhibited apoptosis at 10, 24 and 48 h after IRE ablation. The apoptosis peaked at 10 h after IRE and then declined, suggesting that the ablated tissue rapidly recovered owing to intense metabolic activity. In addition, the electroporated tissues exhibited morphological changes such as pyknosis and karyorrhexis, while histological analysis showed that the blood vessels were preserved. Interestingly, electroporation greatly affected the mucosa and muscularis propria, but not the submucosa and serosa. This study suggests that IRE could potentially be used as a minimally invasive treatment for early gastric cancer that does not exhibit lymph node metastasis or dysplasia.

Veterinary Clinics: Tumor Ablation

Over the past decade, interventional oncology techniques have become integrated into the treatment plans of companion animals with cancer on a regular basis. Although procedures such as stenting are performed commonly, other less frequently utilized techniques for locoregional therapy, such as embolization and ablation, are emerging and demonstrating promise. Tumor ablation techniques are categorized into two subgroups: chemical ablation and energy-based ablation. Increased utilization of ablation will allow for the determination of specific indications and evaluation of outcomes for these techniques.

High-frequency irreversible electroporation is an effective tumor ablation strategy that induces immunologic cell death and promotes systemic anti-tumor immunity

Background

Despite promising treatments for breast cancer, mortality rates remain high and treatments for metastatic disease are limited. High-frequency irreversible electroporation (H-FIRE) is a novel tumor ablation technique that utilizes high-frequency bipolar electric pulses to destabilize cancer cell membranes and induce cell death. However, there is currently a paucity of data pertaining to immune system activation following H-FIRE and other electroporation based tumor ablation techniques.

Methods

Here, we utilized the mouse 4T1 mammary tumor model to evaluate H-FIRE treatment parameters on cancer progression and immune system activation in vitro and in vivo.

Findings

H-FIRE effectively ablates the primary tumor and induces a pro-inflammatory shift in the tumor microenvironment. We further show that local treatment with H-FIRE significantly reduces 4T1 metastases. H-FIRE kills 4T1 cells through non-thermal mechanisms associated with necrosis and pyroptosis resulting in damage associated molecular pattern signaling in vitro and in vivo. Our data indicate that the level of tumor ablation correlates with increased activation of cellular immunity. Likewise, we show that the decrease in metastatic lesions is dependent on the intact immune system and H-FIRE generates 4T1 neoantigens that engage the adaptive immune system to significantly attenuate tumor progression.

Interpretation

Cell death and tumor ablation following H-FIRE treatment activates the local innate immune system, which shifts the tumor microenvironment from an anti-inflammatory state to a pro-inflammatory state. The non-thermal damage to the cancer cells and increased innate immune system stimulation improves antigen presentation, resulting in the engagement of the adaptive immune system and improved systemic anti-tumor immunity.

The Role of Liver-Directed Therapy in Metastatic Colorectal Cancer

Purpose of Review

Colorectal cancer liver metastasis is a major clinical problem, and surgical resection is the only potentially curative treatment. We seek to discuss various liver-directed therapy modalities and explore their roles in the evolving realm of treatment strategies for metastatic colorectal cancer.

Recent Findings

Clinical outcomes for patients with colorectal cancer liver metastases have improved as more patients undergo potentially curative resection and as the armamentarium of systemic treatment and liver-directed therapies continues to expand. Liver-directed therapies have been developed as adjuncts to improve resectability, employed in the adjuvant setting to potentially reduce local recurrence rates, and utilized in the palliative setting with the aim to improve overall survival.

Summary

Ongoing research is expected to validate the role of these evolving therapeutic options, and determine how best to sequence and when to apply these therapies.

Irreversible Electroporation in pancreatic ductal adenocarcinoma: Is there a role in conjunction with conventional treatment?

BACKGROUND

The incidence of pancreatic ductal adenocarcinoma (PDAC) is rapidly increasing. Up to 30% of patients present with locally advanced disease and therefore are not candidates for surgery. Locally advanced pancreatic cancer (LAPC) is an emerging entity lacking in level III evidence-based recommendations for its treatment. Currently, systemic chemotherapy is the main treatment for LAPC. However, due to lack of response or disease progression, downsizing of the tumour, making it resectable is successful in only a small proportion of patients. Radiotherapy is often advocated to improve local disease control if there is stability following chemotherapy. Recently, Irreversible Electroporation (IRE), a novel non-thermal ablation technique, has been proposed for the treatment of LAPC.

AIMS AND METHODS

This narrative review aims to explore the potential role and timing for the use of IRE in patients with LAPC.

RESULTS

To date, there is limited and inconsistent level I and II evidence available in the literature regarding the use of IRE for the treatment of PDAC.

DISCUSSION

Although some of the preliminary experience of the use of IRE in patients with LAPC is encouraging, it should only be used after conventional evidence-based treatments and/or within the research context.

Cardiac impact of R-wave triggered irreversible electroporation therapy

BACKGROUND

Irreversible electroporation (IRE) is a novel tumor ablative therapy technique, using electric fields to induce apoptosis in target tissues. Whether these electric pulses of high field strength can cause cardiac damage and/or ablation-induced arrhythmias is unclear.

OBJECTIVE

The purpose of this study was to systematically evaluate the safety of electrocardiogram (ECG)-gated IRE with regard to cardiac side effects.

METHODS

In all patients, 12-lead ECG and signal-averaged ECG (SAECG) recordings were performed before and after IRE and 24-hour Holter recording on the day of the IRE procedure. Venous blood samples (N-terminal pro-brain-type natriuretic peptide [NT-proBNP], high-sensitive troponin I [hsTnI]) were obtained before and 4 and 16 hours after the procedure. Patients with abnormal findings were reevaluated after 3 months.

RESULTS

In total, 26 patients with an oncologic indication for IRE (11 females, mean age 62.9 years) were prospectively enrolled. Nine patients (34.6%) showed an increase in hsTnI and 21 patients (80.8%) an increase in NT-proBNP after ablation. Fifteen patients (57%) developed arrhythmias related to the procedure. One patient, in whom hsTnI and NT-proBNP had increased, developed multiple, nonsustained ventricular tachycardia events. In another patient, atrial fibrillation was triggered twice in 2 separate procedures. Twelve patients had clinically benign arrhythmias. SAECG was negative in all patients.

CONCLUSION

Subclinical myocardial injury and nonfatal cardiac arrhythmias can occur in the context of IRE treatment. Although no sustained cardiac injuries could be found at 3-month follow-up, we propose implementation of a cardiac safety algorithm consisting of cardiac biomarkers and ECG monitoring when IRE is conducted.

Liver-directed therapy for hepatocellular carcinoma

Liver-directed therapy is a critical component of treatment strategies for hepatocellular carcinoma. These therapies included percutaneous image-guided ablation, transarterial chemoembolization, and transarterial radioembolization, and are administered by interventional radiologists. Depending on the stage of disease, a particular treatment modality, or a combination thereof, is expected to be most efficacious in achieving the goals of treatment for a particular patient. This article seeks to review the various liver-directed treatment modalities for treatment of hepatocellular carcinoma, with attention to their efficacy and patient selection criteria.

Midterm Safety and Efficacy of Irreversible Electroporation of Malignant Liver Tumors Located Close to Major Portal or Hepatic Veins

Purpose To investigate the efficacy and safety of irreversible electroporation (IRE) in the treatment of hepatic tumors not suitable for thermal ablation (radiofrequency ablation [RFA] or microwave ablation). Materials and Methods This was an institutional review board-approved prospective study in 29 patients (15 men, 14 women; mean age, 63 years ± 12 [standard deviation]) with 43 primary (n = 8) or secondary (n = 35) malignant liver tumors who underwent computed tomography (CT)-guided IRE. All target tumors were located immediately adjacent to major hepatic veins, portal veins, or both; thus, they were not considered suitable for RFA or microwave ablation. Patients underwent postinterventional CT and magnetic resonance (MR) imaging. Systematic follow-up MR imaging was performed for 24 months on average to assess complete ablation, intrahepatic tumor recurrence, and complications. The 95% confidence intervals (CIs) were determined for the rate of bile duct strictures, incomplete ablation, and tumor recurrence. Results Complete ablation was achieved in 40 (93%; 95% CI: 85, 100) of 43 target tumors, with a safety margin of 5-10 mm, and was confirmed at immediate postinterventional CT and MR imaging. In 13 (33%; 95% CI: 18, 47) of 40 completely ablated tumors, intrahepatic tumor recurrence was observed at 2-18 months. However, only two (15%; 95% CI: 0, 35) of these 13 tumors were observed within the ablation zone. In the remaining 11 (85%; 95% CI: 65, 100), tumor growth was observed alongside the needle tract. None of the two true local recurrences occurred at the site of the vessel. All adjacent vessels remained perfused at follow-up. Five (24%; 95% CI: 5, 39) of 21 patients with target tumors adjacent to portal veins developed mild to moderate cholestasis 2-6 weeks after IRE. Conclusion IRE is useful to avoid incomplete ablation secondary to heat-sink effects and damage to major blood vessels; however, needle tract seeding is observed in 26% of treated tumors, and IRE induces sufficient local heating to bile ducts in 24% of ablations. ^© RSNA, 2017.

MR and CT imaging characteristics and ablation zone volumetry of locally advanced pancreatic cancer treated with irreversible electroporation

OBJECTIVES

To assess specific imaging characteristics after irreversible electroporation (IRE) for locally advanced pancreatic carcinoma (LAPC) with contrast-enhanced (ce)MRI and ceCT, and to explore the correlation of these characteristics with the development of recurrence.

METHODS

Qualitative and quantitative analyses of imaging data were performed on 25 patients treated with percutaneous IRE for LAPC. Imaging characteristics of the ablation zone on ceCT and ceMRI were assessed over a 6-month follow-up period. Contrast ratio scores between pre- and post-treatment were compared. To detect early imaging markers for treatment failure, attenuation characteristics at 6 weeks were linked to the area of recurrence within 6 months.

RESULTS

Post-IRE, diffusion-weighted imaging (DWI)-b800 signal intensities decreased in all cases (p < 0.05). Both ceMRI and ceCT revealed absent or decreased contrast enhancement, with a hyperintense rim on ceMRI. Ablation zone volume increase was noted on both modalities in the first 6 weeks, followed by a decrease (p < 0.05). In the patients developing tumour recurrence (5/25), a focal DWI-b800 hyperintense spot at 6 weeks predated unequivocal recurrence on CT.

CONCLUSION

The most remarkable signal alterations after pancreatic IRE were shown by DWI-b800 and ceMRI. These early imaging characteristics may be useful to establish technical success and predict treatment outcome.

KEY POINTS

• This study describes imaging characteristics after irreversible electroporation (IRE) for pancreatic adenocarcinoma. • Familiarity with typical post-IRE imaging characteristics helps to interpret ablation zones. • Post-IRE, no central and variable rim enhancement are visible on contrast-enhanced imaging. • DWI-b800 may prove useful to predict early tumour recurrence. • Post-IRE examinations reveal an initial volume increase followed by a decrease.

Skin regeneration with all accessory organs following ablation with irreversible electroporation

Skin scar formation is a complex process that results in the formation of dense extracellular matrix (ECM) without normal skin appendages such as hair and glands. The absence of a scarless healing model in adult mammals prevents the development of successful therapies. We show that irreversible electroporation of skin drives its regeneration with all accessory organs in normal adult rats. Pulsed electric fields at 500 V, with 70 μs pulse duration and 1000 pulses delivered at 3 Hz, applied through two electrodes separated by 2 mm lead to massive cell death. However, the ECM architecture of the skin was preserved. Six months after the ablation, the epidermis, sebaceous glands, panniculus carnosus, hair follicles, microvasculature and arrector pili muscle were altogether re-formed in the entire ablated area. These results suggest a key role of the ECM architecture in the differentiation, migration and signalling of cells during scarless wound healing. Copyright © 2016 John Wiley & Sons, Ltd.

Recurrence patterns following irreversible electroporation for hepatic malignancies

BACKGROUND

Irreversible electroporation (IRE) has emerged as a novel, safe ablative therapy for peri-vascular lesions. However, there remains a paucity of data on long-term outcomes.

METHODS

We identified patients who underwent open IRE (1/2011-6/2015) for primary and secondary hepatic malignancies. Local ablation-zone recurrence (LR) was determined by cross-sectional imaging. Cumulative incidence (CumI) of LR was calculated and a competing risks regression assessed factors associated with LR.

RESULTS

Forty patients had 77 lesions treated. The majority of lesions were of colorectal origin (74%). Median tumor size was 1.3 cm (range 0.5-6). Most patients (86%) had prior systemic therapy and 29% received systemic therapy following IRE. With a median follow-up of 25.7 months (range 4.5-58.8 months), 10 lesions in 9 patients recurred locally (CumI: 13.4%, 95%CI: 7.8-22.2%). Median estimated time to LR was not reached and no LR occurred after 19 months. Factors significantly associated with LR included ablation zone size (HR 1.58; 95%CI 1.12-2.23; P = 0.0093) and body mass index (HR 1.21 95%CI 1.10-1.34; P = 0.0001).

CONCLUSION

IRE LR rates were low after the treatment of well selected, small tumors. This technique is useful for lesions in anatomic locations precluding resection or thermal ablation.

Preclinical and clinical evaluation of the liver tumor irreversible electroporation by magnetic resonance imaging

Irreversible electroporation (IRE) is a relatively new technique for tumor ablation. It has shown promising results in difficult cases where surgery is not recommended and delicate anatomic structures are present near or within the tumor. Currently, liver cancer is one of the most common targets for IRE treatment. Pre-operative and post-operative imaging has a key role in IRE procedures and research studies. Although ultrasound is usually the first choice, especially for intra-operative guidance, magnetic resonance imaging (MRI) plays an important role in the visualization and characterization of tumor before and after IRE in clinical and preclinical studies. However, the appearance of liver lesions after IRE with different MRI sequences has never been systematically investigated, and the most common practice is to limit the acquisition protocol to only contrast-enhanced T1-weighted images. In this work, the role of MRI in clinical and preclinical assessment of hepatic tumors treated with IRE is reviewed and discussed.