Irreversible electroporation near the heart: ventricular arrhythmias can be prevented with ECG synchronization. AJR Am J Roentgenol. 2011;196:W330-W335. [PMID: 21343484 DOI: 10.2214/ajr.10.4490]

Low-Voltage Irreversible Electroporation Using a Comb-Shaped Contact Electrode

OBJECTIVE

Irreversible electroporation (IRE) is a less invasive therapy to ablate tumor cells by delivering short intensive electric pulses more than a few kV via needle-like electrodes. For reducing the required voltage for the IRE, a durable comb-shaped miniature electrode was designed to use in contact with the lesion surface for a new method named contact IRE.

METHODS

A miniature electrode was newly fabricated by a fine inkjet patterning and the subsequent etching of a copper-clad polyimide film. A train of 10-μs or 100-μs long electric pulses were applied 90 times at the interval of 1 s to a tissue phantom, and its cross section was observed to measure the necrotized area.

RESULTS

Cell experiments showed that the maximum ablation depth increased as a function of the applied voltage and reached 400 μm at 20 V. Furthermore, insulation of the lateral space between electrode teeth with a resin and administration of adjuvants to reduce the IRE threshold of the cell membrane did increase the ablation depth by 26% and the ablation area by 40%.

CONCLUSION

The miniature electrode developed in this study successfully necrotized cells in a tissue phantom 400 μm deep from the surface with the electric pulses of only 20 V.

SIGNIFICANCE

The contact IRE for the surface of skin and gastrointestinal tract will ablate cutaneous and subcutaneous tumors by applying only several tens of volts.

Elimination of Purkinje Fibers by Electroporation Reduces Ventricular Fibrillation Vulnerability

Background The Purkinje network appears to play a pivotal role in the triggering as well as maintenance of ventricular fibrillation. Irreversible electroporation ( IRE ) using direct current has shown promise as a nonthermal ablation modality in the heart, but its ability to target and ablate the Purkinje tissue is undefined. Our aim was to investigate the potential for selective ablation of Purkinje/fascicular fibers using IRE . Methods and Results In an ex vivo Langendorff model of canine heart (n=8), direct current was delivered in a unipolar manner at various dosages from 750 to 2500 V, in 10 pulses with a 90-μs duration at a frequency of 1 Hz. The window of ventricular fibrillation vulnerability was assessed before and after delivery of electroporation energy using a shock on T-wave method. IRE consistently eradicated all Purkinje potentials at voltages between 750 and 2500 V (minimum field strength of 250-833 V/cm). The ventricular electrogram amplitude was only minimally reduced by ablation: 0.6±2.3 mV ( P=0.03). In 4 hearts after IRE delivery, ventricular fibrillation could not be reinduced. At baseline, the lower limit of vulnerability to ventricular fibrillation was 1.8±0.4 J, and the upper limit of vulnerability was 19.5±3.0 J. The window of vulnerability was 17.8±2.9 J. Delivery of electroporation energy significantly reduced the window of vulnerability to 5.7±2.9 J ( P=0.0003), with a postablation lower limit of vulnerability=7.3±2.63 J, and the upper limit of vulnerability=18.8±5.2 J. Conclusions Our study highlights that Purkinje tissue can be ablated with IRE without any evidence of underlying myocardial damage.

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.

Intrapulmonary Vein Ablation Without Stenosis: A Novel Balloon-Based Direct Current Electroporation Approach

Background

Current thermal ablation methods for atrial fibrillation, including radiofrequency and cryoablation, have a suboptimal success rate. To avoid pulmonary vein (PV) stenosis, ablation is performed outside of the PV, despite the importance of triggers inside the vein. We previously reported on the acute effects of a novel direct current electroporation approach with a balloon catheter to create lesions inside the PVs in addition to the antrum. In this study, we aimed to determine whether the effects created by this nonthermal ablation method were associated with irreversible lesions and whether PV stenosis or other adverse effects occurred after a survival period.

Methods and Results

Initial and survival studies were performed in 5 canines. At the initial study, the balloon catheter was inflated to contact the antrum and interior of the PV. Direct current energy was delivered between 2 electrodes on the catheter in ECG‐gated 100 μs pulses. A total of 10 PVs were treated demonstrating significant acute local electrogram diminution (mean amplitude decrease of 61.2±19.8%). After the survival period (mean 27 days), computed tomography imaging showed no PV stenosis. On histologic evaluation, transmural, although not circumferential, lesions were seen in each treated vein. No PV stenosis or esophageal injury was present.

Conclusions

Irreversible, transmural lesions can be created inside the PV without evidence of stenosis after a 27‐day survival period using this balloon‐based direct current ablation approach. These early data show promise for an ablation approach that could directly treat PV triggers in addition to traditional PV antrum ablation.

Plasma membrane depolarization and permeabilization due to electric pulses in cell lines of different excitability

In electroporation-based medical treatments, excitable tissues are treated, either intentionally (irreversible electroporation of brain cancer, gene electrotransfer or ablation of the heart muscle, gene electrotransfer of skeletal muscles), or unintentionally (excitable tissues near the target area). We investigated how excitable and non-excitable cells respond to electric pulses, and if electroporation could be an effective treatment of the tumours of the central nervous system. For three non-excitable and one excitable cell line, we determined a strength-duration curve for a single pulse of 10ns-10ms. The threshold for depolarization decreased with longer pulses and was higher for excitable cells. We modelled the response with the Lapicque curve and the Hodgkin-Huxley model. At 1μs a plateau of excitability was reached which could explain why high-frequency irreversible electroporation (H-FIRE) electroporates but does not excite cells. We exposed cells to standard electrochemotherapy parameters (8×100μs pulses, 1Hz, different voltages). Cells behaved similarly which indicates that electroporation most probably occurs at the level of lipid bilayer, independently of the voltage-gated channels. These results could be used for optimization of electric pulses to achieve maximal permeabilization and minimal excitation/pain sensation. In the future, it should be established whether the in vitro depolarization correlates to nerve/muscle stimulation and pain sensation in vivo.

Irreversible electroporation ablation for atrial fibrillation

Atrial fibrillation (AF) is one of the most important problems in modern cardiology. Thermal ablation therapies, especially radiofrequency ablation (RF), are currently "gold standard" to treat symptomatic AF by localized tissue necrosis. Despite the improvements in reestablishing sinus rhythm using available methods, both success rate and safety are limited by the thermal nature of procedures. Thus, while keeping the technique in clinical practice, safer and more versatile methods of removing abnormal tissue are being investigated. This review focuses on irreversible electroporation (IRE), a nonthermal ablation method, which is based on the unrecoverable permeabilization of cell membranes caused by short pulses of high voltage/current. While still in its preclinical steps for what concerns interventional cardiac electrophysiology, multiple studies have shown the efficacy of this method on animal models. The observed remodeling process shows this technique as tissue specific, triggering apoptosis rather than necrosis, and safer for the structures adjacent the myocardium. So far, proposed IRE methodologies are heterogeneous. The number of devices (both generators and applicators), techniques, and therapeutic goals impair the comparability of performed studies. More questions regarding systemic safety and optimal processes for AF treatment remain to be answered. This work provides an overview of the electroporation process, and presents different results obtained by cardiology-oriented research groups that employ IRE ablation, with focus of AF-related targets. This contribution on the topic aspires to be a practical guide to approach IRE ablation for cardiac arrhythmias, and to highlight controversial features and existing knowledge, to provide background for future improved experimentation with IRE in arrhythmology.

In vivo evaluation of bronchial injury of irreversible electroporation in a porcine lung ablation model by using laboratory, pathological, and CT findings

Irreversible electroporation (IRE) creates permanent pores in the cell membrane, leading to irreversible cell death. In this study, the impact of IRE on bronchial injury was comprehensively examined in a timed series study. Altogether, 8 Bama miniature pigs were included in this study and were randomly assigned to experimental and control groups. The experimental group underwent IRE that was guided and monitored by spiral computed tomography (CT). The monopole probe of the IRE was positioned at the right pulmonary hilum. Specimens were collected at 0 h, 2 h, 2 d, 7 d, and 14 d after the IRE procedure for a pathological examination. A small amount of needle-tract bleeding occurred in two animals, and mild pneumothorax occurred in another. IRE can elicit acute bronchial inflammation, bleeding, and mucosal injury, but severe complications were not found. Pathological examinations and transmission electron microscopy (TEM) showed dead vascular epithelium cells in the region of the ablation, while the bronchioli and the vascular extracellular matrix were preserved. At 2 hours post-IRE, there were marked increases in bronchoalveolar macrophages (P<0.001), but the inflammation could recover after 14 days and showed no statistical significance when compared with the control group at the same time. In conclusion, CT-guided IRE ablation can elicit acute but recoverable bronchial inflammation, bleeding, and mucosal injury in porcine lung tissues. However, longer follow-up is still required to establish an evaluation of the long-term safety.

High-voltage pulsed electric field plus photodynamic therapy kills breast cancer cells by triggering apoptosis

This study evaluated the effects and mechanism of action of combining irreversible electroporation (IRE) and photodynamic therapy (PDT) in breast cancer cells in vitro and in vivo. Jin's formula was used to assess killing efficacy of different IRE+PDT dosing combinations in breast cancer MCF-7 cells. Flow cytometry, high-content imaging, and confocal laser scanning microscopy were used to detect apoptosis. qRT-PCR and western blotting were used to evaluate expression of apoptosis-related genes and proteins. IRE+PDT combination therapy was administered to BALB/C mice with breast cancer tumors in vivo; tumor size was used to assess treatment efficacy. Killing mechanisms were examined using transmission electron microscopy and immunohistochemistry. We found that IRE+PDT combination therapy produced significant synergistic killing effects in breast cancer cells (highest Jin q value of 1.32). Early apoptosis rates were significantly higher in the IRE+PDT group (16.0%) than in IRE-alone (7.6%) and PDT-alone (4.6%) groups (P<0.05). qRT-PCR showed higher Caspase-1, -3, -5, -6, -7, -8, and -9 and TNFRSF1A expression with IRE+PDT than with control. Western blots showed increased cleaved Caspase-3, -7, and -9, and PARP levels in the IRE+PDT group. In vivo tumor suppression rate for IRE (1200 V)+PDT (10 mg/kg) was 68.3%. Combination therapy produced the most obvious apoptosis effects. Compared with controls, the IRE+PDT group exhibited lower new blood vessel (VEGF, CD31), metastasis (TGF-β), and cell proliferation (Ki-67) indicators and higher inflammation indicator (TNF-α) 1 day post-treatment. Thus, combining IRE and PDT enhanced their anti-tumor effects in breast cancer, and apoptosis played a key role in this process.

Irreversible Electroporation in Hepatopancreaticobiliary Tumours

Hepatopancreaticobiliary tumours are often diagnosed at an advanced disease stage, in which encasement or invasion of local biliary or vascular structures has already occurred. Irreversible electroporation (IRE) is an image-guided tumour ablation technique that induces cell death by exposing the tumour to high-voltage electrical pulses. The cellular membrane is disrupted, while sparing the extracellular matrix of critical tubular structures. The preservation of tissue integrity makes IRE an attractive treatment option for tumours in the vicinity of vital structures such as splanchnic blood vessels and major bile ducts. This article reviews current data and discusses future trends of IRE for hepatopancreaticobiliary tumours.

Optimization of Electrode Configuration and Pulse Strength in Irreversible Electroporation for Large Ablation Volumes Without Thermal Damage

The aim of this study was to analyze five factors that are responsible for the ablation volume and maximum temperature during the procedure of irreversible electroporation (IRE). The five factors used in this study were the pulse strength (U), the electrode diameter (B), the distance between the electrode and the center (D), the electrode length (L), and the number of electrodes (N). A validated finite element model (FEM) of IRE was built to collect the data of the ablation volume and maximum temperature generated in a liver tissue. Twenty-five experiments were performed, in which the ablation volume and maximum temperature were taken as response variables. The five factors with ranges were analyzed to investigate their impacts on the ablation volume and maximum temperature, respectively, using analysis of variance. Response surface method (RSM) was used to optimize the five factors for the maximum ablation volume without thermal damage (the maximum temperature ≤ 50 °C for 90 s). U and L were found with significant impacts on the ablation volume (P < 0.001, and P = 0.009, respectively) while the same conclusion was not found for B, D and N (P = 0.886, P = 0.075 and P = 0.279, respectively). Furthermore, U, D, and N had the significant impacts on the maximum temperature with P < 0.001, P < 0.001, and P = 0.003, respectively, while same conclusion was not found for B and L (P = 0.720 and P = 0.051, respectively). The maximum ablation volume of 2952.9960 mm3 without thermal damage can be obtained by using the following set of factors: U = 2362.2384 V, B = 1.4889 mm, D = 7 mm, L = 4.5659 mm, and N = 3. The study concludes that both B and N have insignificant impacts (P = 0.886, and P = 0.279, respectively) on the ablation volume; U has the most significant impact (P < 0.001) on the ablation volume; electrode configuration and pulse strength in IRE can be optimized for the maximum ablation volume without thermal damage using RSM.

Electrochemotherapy as a New Modality in Interventional Oncology: A Review

Electroporation is a well-known phenomenon that occurs at the cell membrane when cells are exposed to high-intensity electric pulses. Depending on electric pulse amplitude and number of pulses, applied electroporation can be reversible with membrane permeability recovery or irreversible. Reversible electroporation is used to introduce drugs or genetic material into the cell without affecting cell viability. Electrochemotherapy refers to a combined treatment: electroporation and drug injection to enhance its cytotoxic effect up to 1000-fold for bleomycin. Since several years, electrochemotherapy is gaining popularity as minimally invasive oncologic treatment. The adoption of electrochemotherapy procedure in interventional oncology poses several unsolved questions, since suitable tumor histology and size as well as therapeutic efficacy still needs to be deepen. Electrochemotherapy is usually applied in palliative settings for the treatment of patients with unresectable tumors to relieve pain and ameliorate quality of life. In most cases, it is used in the treatment of advanced stages of neoplasia when radical surgical treatment is not possible (eg, due to lesion location, size, and/or number). Further, electrochemotherapy allows treating tumor nodules in the proximity of important structures like vessels and nerves as the treatment does not involve tissue heating. Overall, the safety profile of electrochemotherapy is favorable. Most of the observed adverse events are local and transient, moderate local pain, erythema, edema, and muscle contractions during electroporation. The aim of this article is to review the recent published clinical experiences of electrochemotherapy use in deep-seated tumors with particular focus on liver cases. The principle of electrochemotherapy as well as the application to cutaneous metastases is briefly described. A short insight in the treatment of bone metastases, unresectable pancreas cancer, and soft tissue sarcoma will be given. Preclinical and clinical studies on treatment efficacy with electrochemotherapy of hepatic lesions and safety of the procedure adopted are discussed.

Catheter-based endobronchial electroporation is feasible for the focal treatment of peribronchial tumors

OBJECTIVE

To evaluate the feasibility of catheter-based endobronchial electroporation for the treatment of peribronchial tumors and assess the incidence of treatment-related adverse events.

METHODS

Cytotoxicity of electroporation with or without cisplatin or gefitinib was assessed in vitro with lung cancer and normal cell lines. A novel catheter was designed for endobronchial electroporation, and computer simulations were used to predict in vivo treatment effects. Electroporation with the test catheter was performed (2000 V, 70 pulses) in the main bronchus of 8 pigs at 11 locations. Computed tomography imaging was performed before they were killed at 4 hours (6 animals) or 4 weeks (2 animals) posttreatment. Treated airway and surrounding parenchyma were compared with sham treatment via gross and histopathology.

RESULTS

Significant cell death due to electroporation and increased cytotoxicity in combination with cisplatin or gefitinib were observed in cancer cells only (P < .05). Simulations predicted penetrative electroporation of peribronchial parenchyma without tissue heating. Electric pulse delivery in vivo induced transient venous and bronchial spasms that resolved without intervention. Cross-sectional measurement of electroporation effects on computed tomography (14.4 ± 1.4 by 10.5 ± 1.3 mm) and gross pathology (17.2 ± 3.0 by 8.8 ± 0.6 mm) were representative of values predicted by simulation (P < .001). Cell death due to irreversible electroporation was observed in bronchial and parenchymal tissue in acute tissue samples. Treated lung rapidly recovered from the effects of electroporation without change in bronchial patency at 4 weeks posttreatment.

CONCLUSIONS

Catheter-based endobronchial electroporation is a reproducible technique that can be used to treat peribronchial tumors in combination with cisplatin, without affecting patency of the treated bronchus.

Irreversible Electroporation: A Novel Ultrasound-guided Modality for Non-thermal Tumor Ablation

Ultrasound-guided tumor ablation techniques have been proven to be highly effective and minimally invasive in the treatment of many diseases. Traditional approaches to ablation include microwave and radiofrequency techniques, cryotherapy, and high-intensity focused ultrasound. However, these methods are prone to heat-sink effects that can diminish the effectiveness of treatment and damage adjacent structures, such as bile ducts, blood vessels, the gallbladder, or bowel. Irreversible electroporation (IRE) is a non-thermal ablation modality that induces cell apoptosis through the application of high-voltage current. IRE is not limited by many of the limitation which affects conventional tumor ablation techniques, and is particularly useful in treating sensitive areas of the body. The article reviews the basics of ultrasound-guided technology, including its clinical applications and effectiveness in the treatment of tumors.

Physical and Chemical Enhancement of and Adaptive Resistance to Irreversible Electroporation of Pancreatic Cancer

Irreversible electroporation (IRE) can be used to treat cancer by electrical pulses, with advantages over traditional thermal approaches. Here we assess for the first time the IRE response of pancreatic cancer, one of the deadliest forms of cancer, both in vitro and in vivo. We demonstrate that both established and primary cancer cell lines can be destroyed by IRE, but with differential susceptibility and thresholds. We further demonstrate in vitro that viability for a given IRE dose can vary with the local chemistry as outcomes were shown to depend on suspending medium and reduction of glucose in the media significantly improved IRE destruction. Data here also demonstrate that repeated IRE treatments can lead to adaptive resistance in pancreatic carcinoma cells thereby reducing subsequent treatment efficacy. In addition, we demonstrate that physical enhancement of IRE, by re-arranging the pulse sequences without increasing the electrical energy delivered, achieve reduced viability in vitro and decreased tumor growth in an in vivo xenograft model. Together, these results show that IRE can destroy pancreatic cancer in vitro and in vivo, that there are both chemical and physical enhancements that can improve tumor destruction, and that one should guard against adaptive resistance when performing repeated treatments.

Ablation with irreversible electroporation in patients with advanced perihilar cholangiocarcinoma (ALPACA): a multicentre phase I/II feasibility study protocol

INTRODUCTION

The majority of patients with perihilar cholangiocarcinoma (PHC) has locally advanced disease or distant lymph node metastases on presentation or exploratory laparotomy, which makes them not eligible for resection. As the prognosis of patients with locally advanced PHC or lymph node metastases in the palliative setting is significantly better compared with patients with organ metastases, ablative therapies may be beneficial. Unfortunately, current ablative options are limited. Photodynamic therapy causes skin phototoxicity and thermal ablative methods, such as stereotactic body radiation therapy and radiofrequency ablation, which are affected by a heat/cold-sink effect when tumours are located close to vascular structures, such as the liver hilum. These limitations may be overcome by irreversible electroporation (IRE), a relatively new ablative method that is currently being studied in several other soft tissue tumours, such as hepatic and pancreatic tumours.

METHODS AND ANALYSIS

In this multicentre phase I/II safety and feasibility study, 20 patients with unresectable PHC due to vascular or distant lymph node involvement will undergo IRE. Ten patients who present with unresectable PHC will undergo CT-guided percutaneous IRE, whereas ultrasound-guided IRE will be performed in 10 patients with unresectable tumours detected at exploratory laparotomy. The primary outcome is the total number of clinically relevant complications (Common Terminology Criteria for Adverse Events, score of≥3) within 90 days. Secondary outcomes include quality of life, tumour response, metal stent patency and survival. Follow-up will be 2 years.

ETHICS AND DISSEMINATION

The protocol has been approved by the local ethics committees. Data and results will be submitted to a peer-reviewed journal.

CONCLUSION

The Ablation with irreversible eLectroportation in Patients with Advanced perihilar CholangiocarcinomA (ALPACA) study is designed to assess the feasibility of IRE for advanced PHC. The main purpose is to inform whether a follow-up trial to evaluate safety and effectiveness in a larger cohort would be feasible.

Case report: Irreversible electroporation for locally advanced pancreatic cancer

•

Locally advanced pancreas cancer (LAPC) has minimal options for local control.

•

Irreversible electroporation (IRE) can potentially improve local control for LAPC.

•

We present a case of IRE with literature review and risks and benefits of IRE.

•

Future studies are needed to clarify which patients may benefit most from IRE.

Introduction

For patients with pancreatic adenocarcinoma who are not candidates for surgical resection, long-term survival is poor, even with currently available systemic and radiation therapy options. However, for those with locally advanced disease who do not have distant metastasis, locoregional control of the tumor has the potential to improve long-term outcomes. A newly developed technology, irreversible electroporation, has advantages over traditional thermal ablation with unresectable cancers in this location.

Presentation of case

In our case report, we describe the first patient treated with irreversible electroporation at our institution for locally advanced pancreatic cancer. The patient is a 63-year-old man who had a partial response to standard chemotherapy and radiation, but was found on operative assessment to have persistently unresectable disease. He therefore underwent irreversible electroporation to the pancreatic mass. His postoperative course was complicated by delayed gastric emptying and wound infection. Three months after surgery, he had no evidence of distant or recurrent disease.

Discussion

Irreversible electroporation for locally advanced pancreatic cancer is an emerging technique which attempts to improve local control of locally advanced, non-metastatic pancreatic cancer. Early data have demonstrated the potential for improved long-term survival in these patients, although further studies are needed to confirm safety and efficacy of this technique.

Conclusion

While there is a positive outlook for the use of irreversible electroporation for locally advanced pancreas cancer, there remain some uncertainties surrounding this therapy, which underscores the importance of future research in this area.

Treatment of Cancer In Vitro Using Radiation and High-Frequency Bursts of Submicrosecond Electrical Pulses

High-frequency irreversible electroporation (H-FIRE) is an emerging cancer therapy, which uses bursts of short duration, alternating polarity, high-voltage electrical pulses to focally ablate tumors. Here, we present a preliminary investigation of the combinatorial effects of H-FIRE and ionizing radiation. In vitro cell cultures were exposed to bursts of 500 ns pulses and single radiation doses of 2 or 20 Gy then analyzed for 14 days. H-FIRE and radiation therapy (RT) appear to induce different delayed cell death mechanisms and in all treatment groups combinatorial therapy resulted in lower overall viabilities. These results indicate that in vivo investigation of the antitumor efficacy of combined H-FIRE and RT is warranted.

Breast tissue ablation with irreversible electroporation in rabbits: A safety and feasibility study

Background and aim

Irreversible electroporation (IRE) was confirmed to control several solid tumors effectively in vivo. Our preclinical study aimed to assess the feasibility and safety of IRE in the breast of rabbit.

Methods

Thirty New Zealand white rabbits were randomly divided into 3 groups of 10 rabbits (control group, IRE group A, and B). Two mono-electrode needles were inserted into the breast tissue by percutaneous puncture. Electrocardiogram and vital signs were monitored before, during, and after ablation. Histopathology, immunohistochemistry, and transmission electron microscopy were examined at 0 hours, 12 hours, 24 hours, 4 days, 7 days, 14 days, and 28 days after ablation.

Results

All the rabbits survived the procedure with no significant adverse effects. Intra-operative ventricular arrhythmias occurred in 1 rabbit from IRE group B and was immediately relieved after ablation. Reversible subcutaneous hemorrhage was observed in 8 rabbits from IRE group A and 7 rabbits from IRE group B. No skin was burnt, however, pectoralis major muscle injuries were found in all rabbits. Histopathological and ultrastructural examination revealed the coexistence of cell necrosis and apoptosis. HE, TUNEL, and Masson staining revealed breast tissue injury and the recovery of damage by fibrous tissue and granulation tissue. Notably, the structures of mammary gland lobules and interstitial components of the breasts were well preserved.

Conclusions

Our study suggests that IRE destroys breast cancer while effectively preserving the skin, the structure of mammary gland lobules, and interstitial components. IRE may be a promising technique to locally control breast cancer and to maintain the esthetic of the breast.

Decision Making: Thermal Ablation Options for Small Renal Masses

Renal cell carcinoma is a relatively common tumor, with an estimated 63,000 new cases being diagnosed in the United States in 2016. Surgery, be it with partial or total nephrectomy, is considered the mainstay of treatment for many patients. However, those patients with small renal masses, typically less than 3 to 4 cm in size who are deemed unsuitable for surgery, may be suitable for percutaneous thermal ablation. We review the various treatment modalities, including radiofrequency ablation, microwave ablation, and cryoablation; discuss the advantages and disadvantages of each method; and review the latest data concerning the performance of the various ablative modalities compared with each other, and compared with surgery.

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.

Bipolar Microsecond Pulses and Insulated Needle Electrodes for Reducing Muscle Contractions During Irreversible Electroporation

OBJECTIVE

To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo.

METHODS

An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer.

RESULTS

With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined.

CONCLUSION

This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction.

SIGNIFICANCE

The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE.

The role of the irreversible electroporation in the hepato-pancreatico-biliary surgery

Irreversible electroporation is a novel technique growing in popularity over the last years among the ablative modalities. Its unique action mechanism produces irreversible nanopores in the membrane of the cell leading to apoptosis; therefore irreversible electroporation can be used to ablate substantial volumes of tissue without the undesirable thermal effects as the "heat sink effect". Moreover the extracellular matrix is left unperturbed, thus sparing the structural architecture of surrounding structures such as bile ducts and blood vessels. In the last years its use has been widespread in both liver and pancreatic ablation. Irreversible electroporation has shown its safety with however some caution, feasibility and favorable outcomes in clinical settings such as unresectable locally advanced disease in which the surgical and therapeutic options are very limited.

Percutaneous electrochemotherapy in the treatment of portal vein tumor thrombosis at hepatic hilum in patients with hepatocellular carcinoma in cirrhosis: A feasibility study

AIM

To treated with electrochemotherapy (ECT) a prospective case series of patients with liver cirrhosis and Vp3-Vp4- portal vein tumor thrombus (PVTT) from hepatocellular carcinoma (HCC), in order to evaluate the feasibility, safety and efficacy of this new non thermal ablative technique in those patients.

METHODS

Six patients (5 males and 1 female), aged 61-85 years (mean age, 70 years), four in Child-Pugh A and two in Child-Pugh B class, entered our study series. All patients were studied with three-phase computed tomography (CT), contrast enhanced ultrasound (CEUS) and ultrasound-guided percutaneous biopsy of the thrombus before ECT. All patients underwent ECT treatment (Cliniporator Vitae^®, IGEA SpA, Carpi, Modena, Italy) of Vp3-Vp4 PVTT in a single session. At the end of the procedure a post-treatment biopsy of the thrombus was performed. Scheduled follow-up in all patients entailed: CEUS within 24 h after treatment; triphasic contrast-enhanced CT and CEUS at 3 mo after treatment and every six months thereafter.

RESULTS

Post-treatment CEUS showed complete absence of enhancement of the treated thrombus in all cases. Post-treatment biopsy showed apoptosis and necrosis of tumor cells in all cases. The follow-up ranged from 9 to 20 mo (median, 14 mo). In 2 patients, the follow-up CT and CEUS demonstrated complete patency of the treated portal vein. Other 3 patients showed a persistent avascular non-tumoral shrinked thrombus at CEUS and CT during follow-up. No local recurrence was observed at follow-up CT and CEUS in 5/6 patients. One patient was lost to follow-up because of death from gastrointestinal hemorrage 5 wk after ECT.

CONCLUSION

In patients with cirrhosis, ECT seems effective and safe for curative treatment of Vp3-Vp4 PVTT from HCC.

Pulmonary Microwave Ablation Near the Heart: Antenna Positioning Can Mitigate Cardiac Complications in a Porcine Model

Purpose To determine how close to the heart pulmonary microwave ablation can be performed without causing cardiac tissue injury or significant arrhythmia. Materials and Methods The study was performed with approval from the institutional animal care and use committee. Computed tomographic fluoroscopically guided microwave ablation of the lung was performed in 12 swine. Antennas were randomized to either parallel (180° ± 20°) or perpendicular (90° ± 20°) orientation relative to the heart surface and to distances of 0-10 mm from the heart. Ablations were performed at 65 W for 5 minutes or until a significant arrhythmia (asystole, heart block, bradycardia, supraventricular or ventricular tachycardia) developed. Heart tissue was evaluated with vital staining and histologic examination. Data were analyzed with mixed effects logistic regression, receiver operating characteristic curves, and the Fisher exact test. Results Thirty-four pulmonary microwave ablations were performed with the antenna a median distance of 4 mm from the heart in both perpendicular (n = 17) and parallel (n = 17) orientation. Significant arrhythmias developed during six (18%) ablations. Cardiac tissue injury occurred with 17 ablations (50%). Risk of arrhythmia and tissue injury decreased with increasing antenna distance from the heart with both antenna orientations. No cardiac complication occurred with a distance of greater than or equal to 4.4 mm from the heart. The ablation zone extended to the pleural surface adjacent to the heart in 71% of parallel and 17% of perpendicular ablations performed 5-10 mm from the heart. Conclusion Microwave lung ablations performed more than or equal to 5 mm from the heart were associated with a low risk of cardiac complications. ^© RSNA, 2016.

Optimizing Irreversible Electroporation Ablation with a Bipolar Electrode

PURPOSE

To optimize single-insertion bipolar irreversible electroporation (IRE) by characterizing effects of electric parameters and controlling tissue electric properties in a porcine model.

MATERIALS AND METHODS

Single-insertion electrode bipolar IRE was performed in 28 in vivo pig livers (78 ablations). First, effects of voltage (2,700-3,000 V), number of pulses, repeated cycles (1-6 cycles), and pulse width (70-100 µs) were studied. Next, electric conductivity was altered by instillation of hypertonic and hypotonic fluids. Finally, effects of thermal stabilization were assessed using internal electrode cooling. Treatment effect was evaluated 2-3 hours after IRE. Dimensions were compared and subjected to statistical analysis.

RESULTS

Delivering 3,000 V at 70 µs for a single 90-pulse cycle yielded 3.8 cm ± 0.4 × 2.0 cm ± 0.3 of ablation. Applying 6 cycles of energy increased ablation to 4.5 cm ± 0.4 × 2.6 cm ± 0.3 (P < .001). Further increasing pulse lengths to 100 µs (6 cycles) increased ablation to 5.0 cm ± 0.4 × 2.9 cm ± 0.3 (P < .001) but resulted in electric spikes and system crashes in 40%-50% of cases. Increasing tissue electric conductivity via hypertonic solution instillation in surrounding tissues increased frequency of generator crashes, whereas continuous instillation of distilled water eliminated this arcing phenomenon but reduced ablation to 2.3 cm ± 0.1. Controlled instillation of distilled water when electric arcing was suspected from audible popping produced ablations of 5.3 cm ± 0.6 × 3.1 cm ±0.3 without crashes. Finally, 3.1 cm ± 0.1 short-axis ablation was achieved without system crashes with internal electrode perfusion at 37°C versus 2.3 cm ± 0.1 with 4°C-10°C perfusion (P < .001).

CONCLUSIONS

Bipolar IRE ablation zones can be increased with repetitive high voltage and greater pulse widths accompanied by either judicious instillation of hypotonic fluids or internal electrode perfusion to minimize unwanted electric arcing.

Intraoperative adverse events during irreversible electroporation-a call for caution

BACKGROUND

Irreversible electroporation is increasingly used for treatment of solid tumors, but safety data remain scarce. This study aimed to describe intraoperative adverse events associated with irreversible electroporation in patients undergoing solid tumor ablation.

METHODS

We analyzed demographic and intraoperative data for patients (n = 43) undergoing irreversible electroporation for hepato-pancreato-biliary and retroperitoneal malignancies (2012 to 2015). Adverse events were defined as cardiac, surgical, or equipment-related.

RESULTS

Adverse events (n = 20, 47%) were primarily cardiac (90%, n = 18), including blood pressure elevation (77%, n = 14/18) and arrhythmia (16%, n = 7/43). All but one was managed medically, 1 patient with arrhythmia required termination of ablation. Bleeding and technical problems with the equipment occurred in 1 patient each. Multivariable analysis revealed previous cardiovascular disease and needle placement close to the celiac trunk associated with increased likelihood for cardiac events.

CONCLUSIONS

Intraoperative cardiac adverse events are common during irreversible electroporation but rarely impair completion of the procedure.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study

BACKGROUND

Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters.

METHODS

Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters.

RESULTS

Phase 1: Direct current (DC) in varying doses (blocking [7-12 μA], electroporation [300-500 μA], ablation [3,000-7,500 μA]), radiofrequency ablation (25-50 W), ultrasound (1.5 MHz), and alcohol (2-5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500-5,000 μA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 μA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium.

CONCLUSION

Percutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

Percutaneous Ablation of Hepatic Tumors Using Irreversible Electroporation: A Prospective Safety and Midterm Efficacy Study in 34 Patients

PURPOSE

To evaluate the safety and efficacy of percutaneous irreversible electroporation (IRE) of primary and secondary liver cancer unsuitable for resection or thermal ablation.

MATERIALS AND METHODS

In this prospective, single-center study, 65 malignant liver tumors (hepatocellular carcinoma, n = 33; cholangiocellular carcinoma, n = 5; colorectal cancer metastasis, n = 22; neuroendocrine cancer metastasis, n = 3; testicular cancer metastasis, n = 2) in 34 patients (27 men, 7 women; mean age, 59.4 y ± 11.2) were treated. Local recurrence-free survival (LRFS) according to the Kaplan-Meier method was evaluated after a median follow-up of 13.9 months.

RESULTS

Median tumor diameter was 2.4 cm ± 1.4 (range, 0.2-7.1 cm). Of 65 tumors, 12 (18.5%) required retreatment because of incomplete ablation (n = 3) or early local recurrence (n = 9). LRFS at 3, 6, and 12 months was 87.4%, 79.8%, and 74.8%. The median time to progressive disease according to modified Response Evaluation Criteria In Solid Tumors was 15.6 months. Overall complication rate was 27.5% with six major complications and eight minor complications. Major complications included diffuse intraperitonal bleeding (n = 1), partial thrombosis of the portal vein (n = 1), and liver abscesses (n = 4). Minor complications were liver hematomas (n = 6) and clinically inapparent pneumothoraces (n = 2).

CONCLUSIONS

IRE showed promising results regarding therapeutic efficacy for the percutaneous treatment of liver tumors; however, significant concerns remain regarding its safety.

Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation): A Review

Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC) accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA) and Irreversible Electroporation (IRE) are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on the use of these techniques have already demonstrated encouraging results in terms of safety and feasibility. Unfortunately, few studies on their efficacy are currently available. Even though some reports on the overall survival are encouraging, randomized studies are still required to corroborate these findings. This study provides an up-to-date overview and a thematic summary of the current available evidence on the application of RFA and IRE on PDAC, together with a comparison of the two procedures.

Diagnostic and therapeutic management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an increasing health problem, representing the second cause of cancer-related mortality worldwide. The major risk factor for HCC is cirrhosis. In developing countries, viral hepatitis represent the major risk factor, whereas in developed countries, the epidemic of obesity, diabetes and nonalcoholic steatohepatitis contribute to the observed increase in HCC incidence. Cirrhotic patients are recommended to undergo HCC surveillance by abdominal ultrasounds at 6-mo intervals. The current diagnostic algorithms for HCC rely on typical radiological hallmarks in dynamic contrast-enhanced imaging, while the use of α-fetoprotein as an independent tool for HCC surveillance is not recommended by current guidelines due to its low sensitivity and specificity. Early diagnosis is crucial for curative treatments. Surgical resection, radiofrequency ablation and liver transplantation are considered the cornerstones of curative therapy, while for patients with more advanced HCC recommended options include sorafenib and trans-arterial chemo-embolization. A multidisciplinary team, consisting of hepatologists, surgeons, radiologists, oncologists and pathologists, is fundamental for a correct management. In this paper, we review the diagnostic and therapeutic management of HCC, with a focus on the most recent evidences and recommendations from guidelines.

Electric Ablation with Irreversible Electroporation (IRE) in Vital Hepatic Structures and Follow-up Investigation

Irreversible electroporation (IRE) with microsecond-pulsed electric fields (μsPEFs) can effectively ablate hepatocellular carcinomas in animal models. This preclinical study evaluates the feasibility and safety of IRE on porcine livers. Altogether, 10 pigs were included. Computed tomography (CT) was used to guide two-needle electrodes that were inserted near the hilus hepatis and gall bladder. Animals were followed-up at 2 hours and at 2, 7 and 14 days post-treatment. During and after μsPEF ablation, electrocardiographs found no cardiovascular events, and contrast CT found no portal vein thrombosis. There was necrosis in the ablation zone. Mild cystic oedema around the gall bladder was found 2 hours post-treatment. Pathological studies showed extensive cell death. There was no large vessel damage, but there was mild endothelial damage in some small vessels. Follow-up liver function tests and routine blood tests showed immediate liver function damage and recovery from the damage, which correlated to the pathological changes. These results indicate that μsPEF ablation affects liver tissue and is less effective in vessels, which enable μsPEFs to ablate central tumour lesions close to the hilus hepatis and near large vessels and bile ducts, removing some of the limitations and contraindications of conventional thermal ablation.

Safety and feasibility of the NanoKnife system for irreversible electroporation ablative treatment of canine spontaneous intracranial gliomas

OBJECT

Irreversible electroporation (IRE) is a novel nonthermal ablation technique that has been used for the treatment of solid cancers. However, it has not been evaluated for use in brain tumors. Here, the authors report on the safety and feasibility of using the NanoKnife IRE system for the treatment of spontaneous intracranial gliomas in dogs.

METHODS

Client-owned dogs with a telencephalic glioma shown on MRI were eligible. Dog-specific treatment plans were generated by using MRI-based tissue segmentation, volumetric meshing, and finite element modeling. After biopsy confirmation of glioma, IRE treatment was delivered stereotactically with the NanoKnife system using pulse parameters and electrode configurations derived from therapeutic plans. The primary end point was an evaluation of safety over the 14 days immediately after treatment. Follow-up was continued for 12 months or until death with serial physical, neurological, laboratory, and MRI examinations.

RESULTS

Seven dogs with glioma were treated. The mean age of the dogs was 9.3 ± 1.6 years, and the mean pretreatment tumor volume was 1.9 ± 1.4 cm3. The median preoperative Karnofsky Performance Scale score was 70 (range 30–75). Severe posttreatment toxicity was observed in 2 of the 7 dogs; one developed fatal (Grade 5) aspiration pneumonia, and the other developed treatment-associated cerebral edema, which resulted in transient neurological deterioration. Results of posttreatment diagnostic imaging, tumor biopsies, and neurological examinations indicated that tumor ablation was achieved without significant direct neurotoxicity in 6 of the 7 dogs. The median 14-day post-IRE Karnofsky Performance Scale score of the 6 dogs that survived to discharge was 80 (range 60–90), and this score was improved over the pretreatment value in every case. Objective tumor responses were seen in 4 (80%) of 5 dogs with quantifiable target lesions. The median survival was 119 days (range 1 to > 940 days).

CONCLUSION

With the incorporation of additional therapeutic planning procedures, the NanoKnife system is a novel technology capable of controlled IRE ablation of telencephalic gliomas.

A review of basic to clinical studies of irreversible electroporation therapy

The use of irreversible electroporation (IRE) for cancer treatment has increased sharply over the past decade. As a nonthermal therapy, IRE offers several potential benefits over other focal therapies, which include 1) short treatment delivery time, 2) reduced collateral thermal injury, and 3) the ability to treat tumors adjacent to major blood vessels. These advantages have stimulated widespread interest in basic through clinical studies of IRE. For instance, many in vitro and in vivo studies now identify treatment planning protocols (IRE threshold, pulse parameters, etc.), electrode delivery (electrode design, placement, intraoperative imaging methods, etc.), injury evaluation (methods and timing), and treatment efficacy in different cancer models. Therefore, this study reviews the in vitro, translational, and clinical studies of IRE cancer therapy based on major experimental studies particularly within the past decade. Further, this study provides organized data and facts to assist further research, optimization, and clinical applications of IRE.

Irreversible electroporation of hepatocellular carcinoma: preliminary report on the diagnostic accuracy of magnetic resonance, computer tomography, and contrast-enhanced ultrasound in evaluation of the ablated area

OBJECTIVE

Irreversible electroporation (IRE) is a new ablation modality. Our purpose was to describe the effectiveness and the safety of the treatment and to evaluate the magnetic resonance imaging (MRI), computed tomography (CT) and contrast-enhanced ultrasound (CEUS) diagnostic accuracy in HCC patients treated with IRE at 1-, 3-, and 6-month follow-up.

MATERIALS AND METHODS

In an 18-month period, we treated 24 HCC lesions in 20 patients unfit for surgery. MRI, CT and CEUS were performed before and one, 3 and 6 month after IRE. We employed the liver-specific contrast medium Primovist (gadolinium ethoxybenzyl dimeglumine) in MRI. After IRE the lesions were classified as responders or non-responders to the treatment according to the mRECIST and the complications were recorded. We evaluated the size, shape, signal intensity (T1-W, T2-W, and DWI) in MRI, dynamic contrast enhancement pattern for CEUS, CT and MRI and signal behavior during the liver-specific phase for MRI.

RESULTS

According to mRECIST, at 1 month MRI and CEUS showed a complete response (CR) in 91.7% of cases (22/24) tumors, while there was partial response (PR) in the remaining 2/24 (8.3%) treated nodules; in CT study all ablated zone appeared as necrotic (CR 100%). The residual viable tumor in MRI and in CEUS study had similar diameter (10 mm). No new HCC were identified from MRI, CT or CEUS. At 3 months MRI and CEUS showed the same results seen after 1 month from the treatment. Twenty-two necrotic lesions, and 2 residual tumors were found (CR = 91.7% and PD = 8.3%). In MRI study the two cases of residual tumor tissue had a diameter of 11 and 12 mm each. At CEUS the diameter of residual HCC was similar to the diameter at 1 month. CT showed 23 necrotic areas and one residual viable tissue in the treated zone, with a diameter of 10 mm (CR = 95.3% and PD = 4.7%). No new foci of HCC were identified from all imaging studies. At 6 months MRI, CEUS, and CT showed 22 necrotic lesions and 2 residual tumors in ablated zone (CR = 91.7% and PD = 8.3%). At MRI the diameters of the two residual viable HCCs were 12 and 14 mm, at CEUS the diameters were 11 and 12 mm, while at CT the diameters were 10 and 10 mm. No statistical difference was evaluated between CR, PR, PD percentage values for MRI, CT and CEUS (p value > 0.05 at Chi-square test). No major vascular complication was recorded after IRE. Six out of 20 patients (30%) showed a transient hepatic intensity difference (THID) area within the normal liver parenchyma adjacent to the treated lesions. Two of the 20 patients (10%) showed an absent concentration of liver-specific contrast medium around the ablation zone. Two patients developed complications, consisting in a peripheral arteriovenous shunt and a segmental dilation of the intrahepatic biliary ducts. We found no statistically significant difference in morphology, size (variation in the largest diameter), signal intensity in T1-weighted images, in T2-weighted images, in DWI and in the related map of the apparent diffusion coefficient (ADC), presence or absence of contrast enhanced during the arterial, portal, and late phase in MRI, CT, and CEUS, and signal characteristic during the liver-specific phase in MRI of the ablation zone at 1, 3, and 6 months.

CONCLUSION

IRE is a feasible, safe and efficient modality in the treatment of patients with non-resectable HCC. We had no major complication, even when the ablated lesion was adjacent to major branches of the portal vein. All images techniques showed similar accuracy during the follow-up at 1, 3, and 6 months in the assessment ablated zone.

Electrochemotherapy of colorectal liver metastases--an observational study of its effects on the electrocardiogram

Background

Electrochemotherapy (ECT) is a combined treatment in which high voltage electroporation (EP) pulses are used to facilitate the uptake of a chemotherapeutic drug into tumor cells, thus increasing antitumor effectiveness of the drug. The effect of ECT of deep-seated tumors located close to the heart on functioning of the heart has not been previously investigated. In this study, we investigate the effects of intra-abdominal ECT of colorectal liver metastases on functioning of the heart during the early post-operative care period.

Methods

For ECT high voltage EP pulses with amplitudes of up to 3000 V and 30 A were delivered in synchronization with electrical activity of the heart. Holter electrocardiographic (ECG) signals were obtained from 10 patients with colorectal liver metastases treated with ECT. ECG was recorded during the periods of 24 hours before and after the surgical procedure involving ECT. Four-hour long night-time ECG segments from both periods exhibiting the highest level of signal stationarity were analyzed and compared. Changes in several ECG and heart rate variability (HRV) parameters were evaluated.

Results

No major heart rhythm changes (i.e., induction of extrasystoles, ventricular tachycardia or fibrillation) or pathological morphological changes (i.e., ST segment changes) indicating myocardial ischemia were found. However, we found several minor statistically significant but clinically irrelevant changes in HRV parameters after ECT procedures: a decrease in median values of the mean NN interval, a decrease in the low-frequency and in the normalized low-frequency component, and an increase in the normalized high-frequency component.

Conclusions

Only minor effects of intra-abdominal ECT treatment on functioning of the heart were found. They were expressed as statistically significant but clinically irrelevant changes in heart rate and long-term HRV parameters and were as such not life-threatening to the patients. The nature of these changes is such that they can be attributed to the known effects of the drugs given to the patients in the post-operative care. Further investigation is still warranted to unambiguously resolve whether ECT with high voltage EP pulses applied in immediate vicinity of the heart is responsible for the observed effects.