Irreversible Electroporation for Hepatic Tumors: Protocol Standardization Using the Modified Delphi Technique

Irreversible Electroporation of the Hepatobiliary System: Current Utilization and Future Avenues

Liver cancer remains a leading cause of cancer-related deaths worldwide despite numerous advances in treatment. While surgical resection remains the gold standard for curative treatment, it is only possible for a minority of patients. Thermal ablation is an effective option for the treatment of smaller tumors; however, its use is limited to tumors that are not located in proximity to sensitive structures due to the heat sink effect and the potential of thermal damage. Irreversible electroporation (IRE) is a non-thermal ablative modality that can deliver targeted treatment and the effective destruction of tumors that are in close proximity to or even surrounding vascular or biliary ducts with minimal damage to these structures. IRE produces short pulses of high-frequency energy which opens pores in the lipid bilayer of cells leading to apoptosis and cell death. IRE has been utilized clinically for over a decade in the treatment of liver cancers with multiple studies documenting an acceptable safety profile and high efficacy rates.

A Systematised Literature Review of Real-World Treatment Patterns and Outcomes in Unresectable Advanced or Metastatic Biliary Tract Cancer

BACKGROUND

Biliary tract cancers are rare aggressive malignancies typically diagnosed when the disease is metastatic or unresectable, precluding curative treatment.

OBJECTIVE

We aimed to identify treatment guidelines, real-world treatment patterns, and outcomes for unresectable advanced or metastatic biliary tract cancers in adult patients.

METHODS

Databases (MEDLINE, Embase, Cochrane Database of Systematic Reviews) were systematically searched between 1 January, 2000 and 25 November, 2021, and supplemented by hand searches. Eligible records were (1) treatment guidelines and (2) observational studies reporting real-world treatment outcomes, for unresectable advanced or metastatic biliary tract cancers. Only studies performed in the UK, Germany, France, Australia, Canada and South Korea were extracted, to moderate the number of records for synthesis while maintaining representation of a wide range of biliary tract cancer incidences.

RESULTS

A total of 66 relevant unique full-text records were extracted, including 16 treatment guidelines and 50 observational studies. Among guidelines, chemotherapies were most strongly recommended at first line (1L); the combination of gemcitabine and cisplatin (GEMCIS) was recommended as the standard of care in 1L. Recommendations for systemic chemotherapy in the second line (2L) conflicted because of uncertainties around survival benefit. Guidelines on further lines of treatment included a range of locoregional modalities and stenting or best supportive care without providing clear recommendations because of data paucity. Fifty observational studies reporting real-world treatment outcomes were extracted, of which 25 (50%) and 9 (18%) reported outcomes in 1L and 2L, respectively; 22 (44%) reported outcomes for treatments described as 'palliative'. In 1L, outcomes for systemic chemotherapy were most frequently described (23/25 studies), and GEMCIS was the most common systemic chemotherapy used (10/23 studies) in line with guidelines. Median overall survival with 1L systemic chemotherapy was < 12 months in most studies (16/23; range 4.7-22.3 months). Most 2L studies (10/11) described outcomes for systemic chemotherapy, most commonly for fluoropyrimidine-based regimen (5/10 studies). Median overall survival with 2L systemic chemotherapy was < 12 months in 5/10 studies (range 4.9-21.5 months). Median progression-free survival was reported more rarely than median overall survival. Some studies with small sample sizes or specifically selected patient populations (e.g. higher performance status, or patients who had already responded to treatment) achieved higher median overall survival.

CONCLUSIONS

At the time of this review, treatment options for unresectable advanced or metastatic biliary tract cancers confer poor real-world survival. For over a decade, GEMCIS remained the 1L standard of care, highlighting the lack of therapeutic innovation in this indication and the urgent unmet need for novel treatments with improved outcomes in this aggressive condition. Additional observational studies are needed to further understand the effectiveness of currently available treatments, as well as newly available therapies including the addition of immunotherapy in the evolving treatment landscape.

Irreversible Electroporation for Liver Metastases from Colorectal Cancer: A Systematic Review

BACKGROUND

Irreversible electroporation (IRE) is a non-thermal form of ablation based on the delivery of pulsed electrical fields. It has been used to treat liver lesions, particularly those in proximity to major hepatic vasculature. The role of this technique in the portfolio of treatments for colorectal hepatic metastases has not been clearly defined. This study undertakes a systematic review of IRE for treatment of colorectal hepatic metastases.

METHODS

The study protocol was registered with the PROSPERO register of systematic reviews (CRD42022332866) and reports in compliance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA). The Ovid MEDLINE^®, EMBASE, Web of Science and Cochrane databases were queried in April 2022. The search terms 'irreversible electroporation', 'colon cancer', 'rectum cancer' and 'liver metastases' were used in combinations. Studies were included if they provided information on the use of IRE for patients with colorectal hepatic metastases and reported procedure and disease-specific outcomes. The searches returned 647 unique articles and the exclusions left a total of eight articles. These were assessed for bias using the methodological index for nonrandomized studies (MINORS criteria) and reported using the synthesis without meta-analysis guideline (SWiM).

RESULTS

One hundred eighty patients underwent treatment for liver metastases from colorectal cancer. The median transverse diameter of tumours treated by IRE was <3 cm. Ninety-four (52%) tumours were adjacent to major hepatic inflow/outflow structures or the vena cava. IRE was undertaken under general anaesthesia with cardiac cycle synchronisation and with the use of either CT or ultrasound for lesion localisation. Probe spacing was less than 3.2 cm for all ablations. There were two (1.1%) procedure-related deaths in 180 patients. There was one (0.5%) post-operative haemorrhage requiring laparotomy, one (0.5%) bile leak, five (2.8%) post-procedure biliary strictures and a zero incidence of post-IRE liver failure.

CONCLUSIONS

This systematic review shows that IRE for colorectal liver metastases can be accomplished with low procedure-related morbidity and mortality. Further prospective study is required to assess the role of IRE in the portfolio of treatments for patients with liver metastases from colorectal cancer.

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

Does the shape of the electric pulse matter in electroporation?

Electric pulses are widely used in biology, medicine, industry, and food processing. Numerous studies indicate that electroporation (EP) is a pulse-dependent process, and the electric pulse shape and duration strongly determine permeabilization efficacy. EP protocols are precisely planned in terms of the size and charge of the molecules, which will be delivered to the cell. In reversible and irreversible EP applications, rectangular or sine, polar or bipolar pulses are commonly used. The usage of pulses of the asymmetric shape is still limited to high voltage and low voltage (HV/LV) sequences in the context of gene delivery, while EP-based applications of ultra-short asymmetric pulses are just starting to emerge. This review emphasizes the importance and role of the pulse shape for membrane permeabilization by EP.

Induction of Bystander and Abscopal Effects after Electroporation-Based Treatments

Simple Summary

The delivery of electric field to tumor cells or nodules induces cell electroporation that allows intracellular delivery of cytotoxic agents and eventually inhibits tumor growth. In this study, we showed that intracellular delivery of calcium ions and anticancer drug bleomycin not only kills the cells but also has a negative bystander effect on indirectly treated cells. We also showed that, when directly applied to one tumor, these treatments can inhibit the growth of a second, non-electroporated tumor.

Abstract

Electroporation-based antitumor therapies, including bleomycin electrotransfer, calcium electroporation, and irreversible electroporation, are very effective on directly treated tumors, but have no or low effect on distal nodules. In this study, we aimed to investigate the abscopal effect following calcium electroporation and bleomycin electrotransfer and to find out the effect of the increase of IL-2 serum concentration by muscle transfection. The bystander effect was analyzed in in vitro studies on 4T1tumor cells, while abscopal effect was investigated in an in vivo setting using Balb/c mice bearing 4T1 tumors. ELISA was used to monitor IL-2 serum concentration. We showed that, similarly to cell treatment with bleomycin electrotransfer, the bystander effect occurs also following calcium electroporation and that these effects can be combined. Combination of these treatments also resulted in the enhancement of the abscopal effect in vivo. Since these treatments resulted in an increase of IL-2 serum concentration only in mice bearing one but not two tumors, we increased IL-2 serum concentration by muscle transfection. Although this did not enhance the abscopal effect of combined tumor treatment using calcium electroporation and bleomycin electrotransfer, boosting of IL-2 serum concentration had a significant inhibitory effect on directly treated tumors.

Biliary complications and efficacy after ablation of peribiliary tumors using irreversible electroporation (IRE) or radiofrequency ablation (RFA)

OBJECTIVE

To evaluate the biliary complication rates and efficacy of peribiliary tumor ablation using irreversible electroporation (IRE) or radiofrequency ablation (RFA).

MATERIAL AND METHODS

This is a retrospective study of 42 consecutive patients with 44 peribiliary tumors (≤5 mm distance between the tumor margin and the primary or secondary bile duct). Data were collected between January 2014 and September 2020 from patients who underwent percutaneous liver ablation using IRE (n = 13) or RFA (n = 31).

RESULTS

The median length of follow-up was 23.1 months. The mean tumor size was 17.2 ± 5.2 mm in IRE vs. 18.4 ± 7.0 mm in RFA (p= .56). Complete tumor ablation was achieved in 100% with a significantly larger ablation zone in the IRE group (3.8 ± 0.3 cm vs. 2.6 ± 0.6 cm, p<.001). Significant biliary complications occurred in one patient (7.7%) of the IRE group and in five patients (16.1%) of the RFA group. Significant risk factors for biliary complications included the RFA procedure (HR 9.71, p=.032) and proximity of the tumor to the bile duct (HR 0.63, p=.048). The local tumor progression (LTP) rates were 7.7% (IRE) vs. 21.5% (RFA) at 1 year, 23.1% (IRE) vs. 32.7% (RFA) at 2 years and 23.1% (IRE) vs. 44% (RFA) at 3 years, respectively (p=.289).

CONCLUSIONS

The IRE and RFA procedures are safe and effective to treat peribiliary liver tumors. However, the RFA may have a higher risk of significant bile duct injury than IRE. The shorter distance between the bile duct and the tumor is a strong risk factor for biliary complications.

Irreversible electroporation for colorectal cancer liver metastasis: a review

Irreversible electroporation (IRE) ablation is gaining popularity over the last decade as a nonthermal alternative to thermal ablation technologies such as radiofrequency ablation (RFA) and Microwave ablation (MWA). This review serves as a practical guide for applying IRE to colorectal cancer liver metastases (CRLM) for interventional radiologists, oncologists, surgeons, and anesthesiologists. It covers patient selection, procedural technique, anesthesia, imaging, and outcomes.

Recurrent Colorectal Liver Metastases in the Liver Remnant After Major Liver Surgery-IRE as a Salvage Local Treatment When Resection and Thermal Ablation are Unsuitable

PURPOSE

To examine the safety and short-term oncologic outcomes of computer-tomography-guided (CT-guided) irreversible electroporation (IRE) of recurrent, irresectable colorectal liver metastases (CRLM) after major hepatectomy deemed unsuitable for thermal ablation.

PATIENTS AND METHODS

Twenty-three patients undergoing CT-guided IRE of recurrent CRLM after major hepatectomy were included in this study. All tumors were located adjacent to sole remaining intrahepatic blood vessels and bile ducts, precluding thermal ablation. Patients underwent systematic clinical and imaging follow-up, including magnetic resonance imaging of the liver at 1-month and 3-month intervals thereafter. Time to local and intrahepatic tumor progression within 12 and 36 months and associated risk factors were assessed using Kaplan Meier and Cox regression analysis, respectively.

RESULTS

Complete ablation with a safety margin of at least 0.5 cm was achieved in 22/23 (95.6%) patients. No vessel injury or thrombosis occurred. Five patients developed moderate biliary stenosis after a median of 4 weeks, without requiring treatment. Local tumor-progression-free rates within 12/36 months were 64%/57.4%, respectively. Intrahepatic-progression-free rate within 12/36 months was 36.4%/19.5%, respectively. Five (23%) patients were tumor-free at the end of follow-up. Multivariate Cox regression analysis did not show any association between local tumor-progression-free rates and patient age, target tumor size, primary tumor side or synchronicity of liver metastases.

CONCLUSION

In this highly selected patient population with local recurrences of CRLM after major surgery, IRE was shown to be a safe salvage treatment option when thermal ablation is unsuitable.

Percutaneous Therapies for Hepatocellular Carcinoma: Evolution of Liver Directed Therapies

Percutaneous ablation is a mainstay of treatment for early stage, unresectable hepatocellular carcinoma (HCC). Recent advances in technology have created multiple ablative modalities for treatment of this common malignancy. The purpose of this review is to familiarize readers with the technical and clinical aspects of both existing and emerging percutaneous treatment options for HCC.

Percutaneous Irreversible Electroporation for Treatment of Small Hepatocellular Carcinoma Invisible on Unenhanced CT: A Novel Combined Strategy with Prior Transarterial Tumor Marking

INTRODUCTION

To explore the feasibility, safety, and efficiency of ethiodized oil tumor marking combined with irreversible electroporation (IRE) for small hepatocellular carcinomas (HCCs) that were invisible on unenhanced computed tomography (CT).

METHODS

A retrospective analysis of the institutional database was performed from January 2018 to September 2018. Patients undergoing ethiodized oil tumor marking to improve target-HCC visualization in subsequent CT-guided IRE were retrieved. Target-HCC visualization after marking was assessed, and the signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNR) were compared between pre-marking and post-marking CT images using the paired t-test. Standard IRE reports, adverse events, therapeutic endpoints, and survival were summarized and assessed.

RESULTS

Nine patients with 11 target-HCCs (11.1-18.8 mm) were included. After marking, all target-HCCs demonstrated complete visualization in post-marking CT, which were invisible in pre-marking CT. Quantitatively, the SNR of the target-HCCs significantly increased after marking (11.07 ± 4.23 vs. 3.36 ± 1.79, p = 0.006), as did the CNR (4.32 ± 3.31 vs. 0.43 ± 0.28, p = 0.023). In sequential IRE procedures, the average current was 30.1 ± 5.3 A, and both the delta ampere and percentage were positive with the mean values of 5.8 ± 2.1 A and 23.8 ± 6.3%, respectively. All procedures were technically successful without any adverse events. In the follow-up, no residual unablated tumor (endpoint-1) was observed. The half-year, one-year, and two-year local tumor progression (endpoint-2) rate was 0%, 9.1%, and 27.3%. The two-year overall survival rate was 100%.

CONCLUSIONS

Ethiodized oil tumor marking enables to demarcate small HCCs that were invisible on unenhanced CT. It potentially allows a safe and complete ablation in subsequent CT-guided IRE.

Irreversible Electroporation (IRE) in Locally Advanced Pancreatic Cancer: A Review of Current Clinical Outcomes, Mechanism of Action and Opportunities for Synergistic Therapy

Locally advanced pancreatic cancer (LAPC) accounts for 30% of patients with pancreatic cancer. Irreversible electroporation (IRE) is a novel cancer treatment that may improve survival and quality of life in LAPC. This narrative review will provide a perspective on the clinical experience of pancreas IRE therapy, explore the evidence for the mode of action, assess treatment complications, and propose strategies for augmenting IRE response. A systematic search was performed using PubMed regarding the clinical use and safety profile of IRE on pancreatic cancer, post-IRE sequential histological changes, associated immune response, and synergistic therapies. Animal data demonstrate that IRE induces both apoptosis and necrosis followed by fibrosis. Major complications may result from IRE; procedure related mortality is up to 2%, with an average morbidity as high as 36%. Nevertheless, prospective and retrospective studies suggest that IRE treatment may increase median overall survival of LAPC to as much as 30 months and provide preliminary data justifying the well-designed trials currently underway, comparing IRE to the standard of care treatment. The mechanism of action of IRE remains unknown, and there is a lack of data on treatment variables and efficiency in humans. There is emerging data suggesting that IRE can be augmented with synergistic therapies such as immunotherapy.

Irreversible Electroporation to Treat Unresectable Colorectal Liver Metastases (COLDFIRE-2): A Phase II, Two-Center, Single-Arm Clinical Trial

Background Irreversible electroporation (IRE), an ablative technique that uses high-voltage electrical pulses, has shown promise for eradicating tumors near critical structures, including blood vessels and bile ducts. Purpose To investigate the efficacy and safety of IRE for colorectal liver metastases (CRLMs) unsuitable for resection or thermal ablation because of proximity to critical structures and for further systemically administered treatments. Materials and Methods Between June 2014 and November 2018, participants with fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET-avid CRLMs measuring 5.0 cm or smaller, unsuitable for partial hepatectomy and thermal ablation, underwent percutaneous or open IRE (ClinicalTrials.gov identifier: NCT02082782). Follow-up included tumor marker assessment and ¹⁸F-FDG PET/CT imaging. For the primary end point to be met, at least 50% of treated participants had to be alive without local tumor progression (LTP) at 12 months, defined as LTP-free survival. Secondary aims were safety, technical success, local control allowing for repeat procedures, disease-free status, and overall survival. Results A total of 51 participants (median age, 67 years [interquartile range, 62-75 years]; 37 men) underwent IRE. Of these 51 participants, 50 with a total of 76 CRLMs (median tumor size, 2.2 cm; range, 0.5-5.4 cm) were successfully treated in 62 procedures; in one participant, treatment was stopped prematurely because of pulse-induced cardiac arrhythmia. With a per-participant 1-year LTP-free survival of 68% (95% CI: 59, 84) according to competing risk analysis, the primary end point was met. Local control following repeat procedures was achieved in 74% of participants (37 of 50). Median overall survival from first IRE was 2.7 years (95% CI: 1.6, 3.8). Twenty-three participants experienced a total of 34 adverse events in 25 of the 62 procedures (overall complication rate, 40%). One participant (2%), who had an infected biloma after IRE, died fewer than 90 days after the procedure (grade 5 adverse event). Conclusion Irreversible electroporation was effective and relatively safe for colorectal liver metastases 5.0 cm or smaller that were unsuitable for partial hepatectomy, thermal ablation, or further systemic treatment. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Goldberg in this issue.