Percutaneous ablation of peribiliary tumors with irreversible electroporation

Electrolysis products, reactive oxygen species and ATP loss contribute to cell death following irreversible electroporation with microsecond-long pulsed electric fields

Membrane permeabilization and thermal injury are the major cause of cell death during irreversible electroporation (IRE) performed using high electric field strength (EFS) and small number of pulses. In this study, we explored cell death under conditions of reduced EFS and prolonged pulse application, identifying the contributions of electrolysis, reactive oxygen species (ROS) and ATP loss. We performed ablations with conventional high-voltage low pulse (HV-LP) and low-voltage high pulse (LV-HP) conditions in a 3D tumor mimic, finding equivalent ablation volumes when using 2000 V/cm 90 pulses or 1000 V/cm 900 pulses respectively. These results were confirmed by performing ablations in swine liver. In LV-HP treatment, ablation volume was found to increase proportionally with pulse numbers, without the substantial temperature increase seen with HV-LP parameters. Peri-electrode pH changes, ATP loss and ROS production were seen in both conditions, but LV-HP treatments were more sensitive to blocking of these forms of cell injury. Increases in current drawn during HV-LP was not observed during LV-HP condition where the total ablation volume correlated to the charge delivered into the tissue which was greater than HV-LP treatment. LV-HP treatment provides a new paradigm in using pulsed electric fields for tissue ablation with clinically relevant volumes.

Percutaneous image-guided ablation for hepatic metastases

The presence of hepatic metastases indicates advanced disease and is associated with significant morbidity and mortality, especially when the hepatic disease is not amenable to locoregional treatments. The primary tumour of origin, the distribution and extent of metastatic disease, the underlying liver reserve, the patient performance status and the presence of comorbidities are factors that determine whether a patient will benefit from hepatectomy or local curative-intent treatments. For patients with metastatic colorectal cancer, the most common primary cancer that spreads to the liver, several studies have demonstrated a survival benefit for patients who can be treated with hepatectomy and/or percutaneous ablation, compared to those treated with chemotherapy alone. Despite advances in surgical techniques increasing the percentage of patients eligible for surgery, most patients have unresectable disease or are poor surgical candidates. Percutaneous ablation can be used to provide local disease control and prolong survival for both surgical and non-surgical candidates. This is typically offered to patients with small hepatic metastases that can be ablated with optimal (≥10 mm) or at least adequate minimum ablation margins (≥5 mm), as high local tumour control rates can be achieved for these patients which are comparable to surgical resection. This review summarizes available evidence and outcomes following percutaneous ablation of the most frequently encountered types of hepatic metastases in the clinical practice of interventional oncology. Patient selection, technical considerations, follow-up protocols and oncologic outcomes are presented and discussed.

Clinical translation of abdominal histotripsy: a review of preclinical studies in large animal models

Histotripsy is an emerging noninvasive, non-thermal, and non-ionizing focused ultrasound (US) therapy that can be used to destroy targeted tissue. Histotripsy has evolved from early laboratory prototypes to clinical systems which have been comprehensively evaluated in the preclinical environment to ensure safe translation to human use. This review summarizes the observations and results from preclinical histotripsy studies in the liver, kidney, and pancreas. Key findings from these studies include the ability to make a clinically relevant treatment zone in each organ with maintained collagenous architecture, potentially allowing treatments in areas not currently amenable to thermal ablation. Treatments across organ capsules have proven safe, including in anticoagulated models which may expand patients eligible for treatment or eliminate the risk associated with taking patients off anti-coagulation. Treatment zones are well-defined with imaging and rapidly resorb, which may allow improved evaluation of treatment zones for residual or recurrent tumor. Understanding the effects of histotripsy in animal models will help inform physicians adopting histotripsy for human clinical use.

Non-Contact Irreversible Electroporation in the Esophagus With a Wet Electrode Approach

Our objective was to develop a technique for performing irreversible electroporation (IRE) of esophageal tumors while mitigating thermal damage to the healthy lumen wall. We investigated noncontact IRE using a wet electrode approach for tumor ablation in a human esophagus with finite element models for electric field distribution, joule heating, thermal flux, and metabolic heat generation. Simulation results indicated the feasibility of tumor ablation in the esophagus using an catheter mounted electrode immersed in diluted saline. The ablation size was clinically relevant, with substantially lesser thermal damage to the healthy esophageal wall when compared to IRE performed by placing a monopolar electrode directly into the tumor. Additional simulations were used to estimate ablation size and penetration during noncontact wet-electrode IRE (wIRE) in the healthy swine esophagus. A novel catheter electrode was manufactured and wIRE evaluated in seven pigs. wIRE was performed by securing the device in the esophagus and using diluted saline to isolate the electrode from the esophageal wall while providing electric contact. Computed tomography and fluoroscopy were performed post-treatment to document acute lumen patency. Animals were sacrificed within four hours following treatment for histologic analysis of the treated esophagus. The procedure was safely completed in all animals; post-treatment imaging revealed intact esophageal lumen. The ablations were visually distinct on gross pathology, demonstrating full thickness, circumferential regions of cell death (3.52 ± 0.89 mm depth). Acute histologic changes were not evident in nerves or extracellular matrix architecture within the treatment site. Catheter directed noncontact IRE is feasible for performing penetrative ablations in the esophagus while avoiding thermal damage.

Role of Percutaneous Ablation in the Management of Intrahepatic Cholangiocarcinoma

Cholangiocarcinoma (CCA) is an invasive cancer accounting for <1% of all cancers and 10-15% of primary liver cancers. Intrahepatic CCA (iCCA) is associated with poor survival rates and high post-surgical recurrence rates whilst most diagnosed patients are not surgical candidates. There is a growing literature suggesting percutaneous ablative techniques for the management of patients with iCCA measuring ≤3 cm with contraindications to surgery as well as for recurrent or residual tumors aiming to provide local cancer treatment and control. Most used ablative therapies for iCCA include radiofrequency and microwave ablation with irreversible electroporation, cryoablation and reversible electroporation (electrochemotherapy) being less commonly encountered techniques. Due to the infiltrative margins of the lesion, there is a need for larger safety margins and ablation zone; multi-apparatus ablation or other variations of the technique such as balloon-assisted approaches can be utilized aiming to increase size of the zone of necrosis. The present review paper focuses upon the current role of percutaneous ablative techniques for the therapeutic management of iCCA. The purpose of this review is to present the current minimally invasive ablative techniques in the treatment of iCCA, including local control and survival rates.

An update on locoregional percutaneous treatment technologies in colorectal cancer liver metastatic disease

INTRODUCTION

Liver-dominant metastatic colorectal cancer is noted in approximately 20%-35% of the patients. Systemic chemotherapy remains the first-line treatment for mCRC, but the prognosis is poor due to liver failure. Novel minimally invasive technologies have enabled the optimization of locoregional treatment options.

AREAS COVERED

This is a comprehensive review of novel locoregional treatment technologies, both percutaneous ablation and transcatheter arterial treatments, which can be used to decrease hepatic disease progression in patients with mCRC. Trans-arterial radioembolization is the most recently developed locoregional treatment for metastatic liver disease, and robust evidence has been accumulated over the past years.

EXPERT OPINION

Image-guided techniques, endovascular and ablative, have gained wide acceptance for the treatment of liver malignancies, in selected patients with non-resectable disease. The optimization of dosimetry and microsphere technological advancement will certainly upgrade the role of liver radioembolization segmentectomy or lobectomy in the upcoming years, due to its curative intent. Also, ablative interventions provide local curative intent, offering significant and sustained local tumor control. Standardization protocols in terms of predictability and reliability using immediate treatment assessment and ablation zone software could further ameliorate clinical outcomes.

Irreversible Electroporation in Pancreatic Cancer-An Evolving Experimental and Clinical Method

Pancreatic cancer has no symptoms until the disease has advanced and is aggressive cancer with early metastasis. Up to now, the only curative treatment is surgical resection, which is possible in the early stages of the disease. Irreversible electroporation treatment offers new hope for patients with unresectable tumors. Irreversible electroporation (IRE) is a type of ablation therapy that has been explored as a potential treatment for pancreatic cancer. Ablation therapies involve the use of energy to destroy or damage cancer cells. IRE involves using high-voltage, low-energy electrical pulses to create resealing in the cell membrane, causing the cell to die. This review summarizes experiential and clinical findings in terms of the IRE applications. As was described, IRE can be a non-pharmacological approach (electroporation) or combined with anticancer drugs or standard treatment methods. The efficacy of irreversible electroporation (IRE) in eliminating pancreatic cancer cells has been demonstrated through both in vitro and in vivo studies, and it has been shown to induce an immune response. Nevertheless, further investigation is required to assess its effectiveness in human subjects and to comprehensively understand IRE's potential as a treatment option for pancreatic cancer.

Ablative Therapy in Non-HCC Liver Malignancy

Surgical extirpation of liver tumors remains a proven approach in the management of metastatic tumors to the liver, particularly those of colorectal origin. Ablative, non-resective therapies are an increasingly attractive primary therapy for liver tumors as they are generally better tolerated and result in far less morbidity and mortality. Ablative therapies preserve greater normal liver parenchyma allowing better post-treatment liver function and are particularly appropriate for treating subsequent liver-specific tumor recurrence. This article reviews the current status of ablative therapies for non-hepatocellular liver tumors with a discussion of many of the clinically available approaches.

The multidisciplinary management of cholangiocarcinoma

Cholangiocarcinoma is a lethal malignancy of the biliary epithelium that can arise anywhere along the biliary tract. Surgical resection confers the greatest likelihood of long-term survivability. However, its insidious onset, difficult diagnostics, and resultant advanced presentation render the majority of patients unresectable, highlighting the importance of early detection with novel biomarkers. Developing liver-directed therapies and emerging targeted therapeutics may offer improved survivability for patients with unresectable or advanced disease. In this article, the authors review the current multidisciplinary standards of care in resectable and unresectable cholangiocarcinoma, with an emphasis on novel biomarkers for early detection and nonsurgical locoregional therapy options.

The Enlargement of Ablation Area by Electrolytic Irreversible Electroporation (E-IRE) Using Pulsed Field with Bias DC Field

Irreversible electroporation (IRE) by high-strength electric pulses is a biomedical technique that has been effectively used for minimally invasive tumor therapy while maintaining the functionality of adjacent important tissues, such as blood vessels and nerves. In general, pulse delivery using needle electrodes can create a reversible electroporation region beyond both the ablation area and the vicinity of the needle electrodes, limiting enlargement of the ablation area. Electrochemical therapy (EChT) can also be used to ablate a tumor near electrodes by electrolysis using a direct field with a constant current or voltage (DC field). Recently, reversible electroporated cells have been shown to be susceptible to electrolysis at relatively low doses. Reversible electroporation can also be combined with electrolysis for tissue ablation. Therefore, the objective of this study is to use electrolysis to remove the reversible electroporation area and thereby enlarge the ablation area in potato slices in vitro using a pulsed field with a bias DC field (constant voltage). We call this protocol electrolytic irreversible electroporation (E-IRE). The area over which the electrolytic effect induced a pH change was also measured. The results show that decreasing the pulse frequency using IRE alone is found to enlarge the ablation area. The ablation area generated by E-IRE is significantly larger than that generated by using IRE or EChT alone. The ablation area generated by E-IRE at 1 Hz is 109.5% larger than that generated by IRE, showing that the reversible electroporation region is transformed into an ablation region by electrolysis. The area with a pH change produced by E-IRE is larger than that produced by EChT alone. Decreasing the pulse frequency in the E-IRE protocol can further enlarge the ablation area. The results of this study are a preliminary indication that the E-IRE protocol can effectively enlarge the ablation area and enhance the efficacy of traditional IRE for use in ablating large tumors.

Needle tract seeding following percutaneous irreversible electroporation for hepatocellular carcinoma

Irreversible electroporation (IRE) is a non-thermal ablative technique for unresectable liver malignancies deemed unsuitable for traditional thermal ablation due to proximity to biliary and/or vascular structures. Needle tract tumour seeding is a well-recognised complication following thermal ablation, while little is known about its risk with IRE use. We present a case of tumour seeding after IRE for unresectable hepatocellular carcinoma in a man in his 70s. The procedure was complicated by bleeding from a pseudoaneurysm, which required coil embolisation and blood transfusion. He initially progressed well, however, imaging at 12 months indicated a new tumour in the right intercostal space along the tract of one of the IRE needles; consistent with seeding. Although the patient subsequently underwent systemic therapy with sorafenib, his disease progressed, and unfortunately he passed away 20 months following IRE. This report adds to mounting evidence of needle tract tumour seeding as a complication following IRE.

Real-Time Temperature Rise Estimation during Irreversible Electroporation Treatment through State-Space Modeling

To evaluate the feasibility of real-time temperature monitoring during an electroporation-based therapy procedure, a data-driven state-space model was developed. Agar phantoms mimicking low conductivity (LC) and high conductivity (HC) tissues were tested under the influences of high (HV) and low (LV) applied voltages. Real-time changes in impedance, measured by Fourier Analysis SpecTroscopy (FAST) along with the known tissue conductivity and applied voltages, were used to train the model. A theoretical finite element model was used for external validation of the model, producing model fits of 95.8, 88.4, 90.7, and 93.7% at 4 mm and 93.2, 58.9, 90.0, and 90.1% at 10 mm for the HV-HC, LV-LC, HV-LC, and LV-HC groups, respectively. The proposed model suggests that real-time temperature monitoring may be achieved with good accuracy through the use of real-time impedance monitoring.

Interventional oncology of liver tumors: how it all started and where are we now

Liver was the very first organ for which interventional procedures were applied for the local treatment of primary and secondary malignancies. In this paper, the history of Interventional Oncology of liver, from the very beginning to the current situation, is summarized, including both percutaneous and intravascular procedures, and together with the evolution of the techniques for image guidance. The main ongoing developments, such as new techniques, combined interventional treatments and association of local interventions with new drugs are briefly described, too.

An overview of the irreversible electroporation for the treatment of liver metastases: When to use it

Tumour ablation is an established therapy for local treatment of liver metastases and hepatocellular carcinoma. Most commonly two different kind of thermic ablation, radiofrequency ablation and microwave ablation, are used in clinical practice. The aim of both is to induce thermic damage to the malignant cells in order to obtain coagulative necrosis of the neoplastic lesions. Our main concerns about these procedures are the collateral thermic damage to adjacent structures and heat-sink effect. Irreversible electroporation (IRE) is a recently developed, non-thermal ablation procedure which works applying short pulses of direct current that generate an electric field in the lesion area. The electric field increase the transmembrane potential, changing its permeability to ions.Irreversible electroporation does not generate heat, giving the chance to avoid the heat-sink effect and opening the path to a better treatment of all the lesions located in close proximity to big vessels and bile ducts. Electric fields produced by the IRE may affect endothelial cells and cholangiocytes but they spare the collagen matrix, preserving re-epithelization process as well as the function of the damaged structures. Purpose of the authors is to identify the different scenarios where CT-guided percutaneous IRE of the liver should be preferred to other ablative techniques and why.

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.

Percutaneous Ablation of Hepatic Tumors at the Hepatocaval Confluence Using Irreversible Electroporation: A Preliminary Study

Background: Tumors at the hepatocaval confluence are difficult to treat, either surgically or ablatively. Methods: A retrospective longitudinal study on patients ineligible for thermal ablation who underwent computed tomography-guided IRE for hepatic tumors at the hepatocaval confluence was conducted. Factors analyzed included patient and tumor characteristics, IRE procedure details, treatment-related complications, and prognosis. Results: Between 2017 and 2021, 21 patients at our institute received percutaneous IRE. Of the 38 lesions, 21 were at the hepatocaval confluence. Complete ablation was achieved in all cases. Local and distant recurrence was observed in 4.8% (1/21) and 42.6% (9/21) of the ablated tumors, respectively. All postcava remained perfused at follow-up, except for 1 (4.8%) hepatic vein near the lesion found to be temporarily occluded and restored within 1 month. The ratio of the maximum diameter of ablation area at 1, 3, and 6 months post procedure compared to that immediately after IRE was 0.68 (0.50–0.84), 0.49 (0.27–0.61), and 0.38 (0.25–0.59), respectively. Progression-free survival of the patients with recurrence was 121 (range, 25–566) days. Four (19.0%) patients died at the end of follow-up with median overall survival of 451.5 (range, 25–716) days. Conclusions: IRE could be a safe and effective treatment for hepatic tumors at the hepatocaval confluence. This article provides valuable prognostic data; further clinical research is needed for better prognosis.

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.

Electroporation and Electrochemotherapy in Gynecological and Breast Cancer Treatment

Gynecological carcinomas affect an increasing number of women and are associated with poor prognosis. The gold standard treatment plan is mainly based on surgical resection and subsequent chemotherapy with cisplatin, 5-fluorouracil, anthracyclines, or taxanes. Unfortunately, this treatment is becoming less effective and is associated with many side effects that negatively affect patients’ physical and mental well-being. Electroporation based on tumor exposure to electric pulses enables reduction in cytotoxic drugs dose while increasing their effectiveness. EP-based treatment methods have received more and more interest in recent years and are the subject of a large number of scientific studies. Some of them show promising therapeutic potential without using any cytotoxic drugs or molecules already present in the human body (e.g., calcium electroporation). This literature review aims to present the fundamental mechanisms responsible for the course of EP-based therapies and the current state of knowledge in the field of their application in the treatment of gynecological neoplasms.

Outcomes of irreversible electroporation (IRE) for perihilar cholangiocarcinoma (ALPACA): a prospective pilot study

PURPOSE

To investigate safety and efficacy of percutaneous or open irreversible electroporation (IRE) in a prospective cohort of patients with locally advanced, unresectable perihilar cholangiocarcinoma (PHC).

MATERIALS AND METHODS

In a multicenter phase I/II study patients with unresectable PHC due to extensive vascular involvement or N2 lymph node metastases or local recurrence after resection for PHC were included and treated by open or percutaneous IRE combined with palliative chemotherapy (current standard of care). Primary outcome was the number of major adverse events occurring within 90 days after IRE (grade ≥3) and the upper-limit was predefined at 60%. Secondary outcomes included technical success rate, hospital stay and overall survival (OS).

RESULTS

Twelve patients (mean age 63±12 years) were treated with IRE. The primary outcome of major adverse event rate was 50% (6 out of 12 patients) and no 90-day mortality was observed. All procedures were technically successful, with no intra-procedural adverse events requiring additional interventions. Median OS from diagnosis was 21 months (95% CI 15-27 months), with a one-year survival rate after IRE of 75%.

CONCLUSION

Percutaneous IRE in selected patients with locally advanced PHC seems feasible, with the major adverse event rate of 50% below the predefined upper safety limit in this prospective study. Future comparative research exploring the efficacy of IRE is warranted.

Irreversible electroporation for liver cancer ablation: A meta analysis

OBJECTIVE

To evaluate the efficacy and safety of IRE in the treatment of hepatic malignant tumors, especially the damage to the gastrointestinal tract, bile ducts, and vital vessels.

METHODS

The relevant literatures published from January 1, 2010 to July 1, 2021 were searched from PubMed and Embase databases. The following keywords were applied: "irreversible electroporation", "IRE", "unresectable Hepa∗ cancer", "ablation" and "ablation therapy".

RESULTS

Twenty-six studies were identified covering 807 participants and 1115 lesions. The complete ablation rate of liver cancer by IRE was 86% (95% CI: 81%-90%). The incidence of IRE-related complications was 23% (95% CI: 17%-28%), but most of them were minor, major complications such as biliary fistula, intestinal fistula and massive hemorrhage were rare.

CONCLUSION

Meta-analysis showed that IRE ablation is safe and effective for liver cancer treatment. Bile duct, intestine and blood vessels adjacent to the tumors are rarely damaged by IRE ablation.

Interventional Radiology Image-Guided Locoregional Therapies (LRTs) and Immunotherapy for the Treatment of HCC

Image-guided locoregional therapies (LRTs) are a crucial asset in the treatment of hepatocellular carcinoma (HCC), which has proven to be characterized by an impaired antitumor immune status. LRTs not only directly destroy tumor cells but also have an immunomodulating role, altering the tumor microenvironment with potential systemic effects. Nevertheless, the immune activation against HCC induced by LRTs is not strong enough on its own to generate a systemic significant antitumor response, and it is incapable of preventing tumor recurrence. Currently, there is great interest in the possibility of combining LRTs with immunotherapy for HCC, as this combination may result in a mutually beneficial and synergistic relationship. On the one hand, immunotherapy could amplify and prolong the antitumoral immune response of LRTs, reducing recurrence cases and improving outcome. On the other hand, LTRs counteract the typical immunosuppressive HCC microenvironment and status and could therefore enhance the efficacy of immunotherapy. Here, after reviewing the current therapeutic options for HCC, we focus on LRTs, describing for each of them the technique and data on its effect on the immune system. Then, we describe the current status of immunotherapy and finally report the recently published and ongoing clinical studies testing this combination.

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.

Ablation Zone Involution of Liver Tumors Is Faster in Patients Treated with Irreversible Electroporation Than Microwave Ablation

Background and Objectives: To compare ablation zone involution following microwave ablation (MWA) or irreversible electroporation (IRE) of liver tumors. Materials and Methods: MWA or IRE performed for colorectal cancer liver metastasis (CRLM) or hepatocellular carcinoma (HCC) during January 2011 to December 2015 were analyzed. Patients with a tumoral response on 1-year follow-up computed tomography (CT) were included. Generalized estimating equations were used to evaluate the differences between the two modalities on ablation zone involution observed on CT at 6 (M6) and 12 months (M12), and on laboratory values (total bilirubin, alanine transaminase, aspartate transaminase, alkaline phosphatase, albumin, and platelets count). The likelihood ratio test was used to assess whether the association between ablation modalities and these outcomes differed over time. Results: Seventeen (17/44, 39%) women and 27 (27/44, 61%) men were included, with 25 HCC (25/44, 57%) and 19 CRLM (19/44, 43%) patients. IRE was used in 9 (9/19, 47%) CRLM and 5 (5/25, 20%) HCC patients, respectively. All other patients had MWA. Ablation zone size and involution between IRE and MWA differed significantly over time (interaction p < 0.01), with a mean of 241.04 vs. 771.08 mm2 (ratio 0.313; 95% CI, 0.165-0.592; p < 0.01) at M6 and 60.47 vs. 589.43 mm2 (ratio 0.103; 95% CI, 0.029-0.365; p < 0.01) at M12. Changes in liver enzymes did not differ significantly between IRE and MWA at both timepoints. Conclusions: Liver tumors treated with IRE underwent faster involution when compared to tumors treated with MWA, but liver enzymes levels were comparable.

Combination of natural killer cell-based immunotherapy and irreversible electroporation for the treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is among the most lethal cancer types despite great advancement in overall survival of the patients over the last decades. Surgical resection or partial hepatectomy has been approved as the curative treatment for early-stage HCC patients however only up to 30% of them are eligible for the procedures. Natural killer (NK) cells are cytotoxic lymphocytes recognized for killing virally infected cells and improving immune functions for defending the body against malignant cells. Although autologous NK cells failed to demonstrate significant clinical benefit, transfer of allogeneic adoptive NK cells arises as a promising approach for the treatment of solid tumors. The immunosuppressive tumor microenvironment and inadequate homing efficiency of NK cells to tumors can inhibit adoptive transfer immunotherapy (ATI) efficacy. However, potential of the NK cells is challenged by the transfection efficiency. The local ablation techniques that employ thermal or chemical energy have been investigated for the destruction of solid tumors for three decades and demonstrated promising benefits for individuals not eligible for surgical resection or partial hepatectomy. Irreversible electroporation (IRE) is one of the most recent minimally invasive ablation methods that destruct the cell within the targeted region through non-thermal energy. IRE destroys the tumor cell membrane by delivering high-frequency electrical energy in short pulses and overcomes tumor immunosuppression. The previous studies demonstrated that IRE can induce immune changes which can facilitate activation of specific immune responses and improve transfection efficiency. In this review paper, we have discussed the mechanism of NK cell immunotherapy and IRE ablation methods for the treatment of HCC patients and the combinatorial benefits of NK cell immunotherapy and IRE ablation.

Image-Guided Ablation for Colorectal Liver Metastasis: Principles, Current Evidence, and the Path Forward

Simple Summary

Colorectal cancer is the fourth most common type of cancer globally. Approximately 20% of patients with colorectal cancer present with synchronous liver metastases, and up to 60% will develop metachronous metastases during the course of the disease. Although liver resection is currently considered the local treatment of choice for colorectal liver metastasis (CLM), less than one-third of patients are eligible for surgery at the time of diagnosis of CLM. Ablation is a well-established, less invasive, locoregional therapy for patients with small CLMs, which has shown favorable oncological outcomes in patients with unresectable CLMs, comparable to those in patients eligible for surgery. The increasing knowledge of factors affecting oncological outcomes has allowed selected patients with resectable small volume CLMs to be treated with thermal ablation with curative intent. The continuous technological evolutions in imaging and image guidance have contributed to this paradigm shift in CLM treatment. The importance of patient selection, patient factors, tumor factors, ablation techniques, and clinical applications is discussed in this article.

Abstract

Image-guided ablation can provide effective local tumor control in selected patients with CLM. A randomized controlled trial suggested that radiofrequency ablation combined with systemic chemotherapy resulted in a survival benefit for patients with unresectable CLM, compared to systemic chemotherapy alone. For small tumors, ablation with adequate margins can be considered as an alternative to resection. The improvement of ablation technologies can allow the treatment of tumors close to major vascular structures or bile ducts, on which the applicability of thermal ablation modalities is challenging. Several factors affect the outcomes of ablation, including but not limited to tumor size, number, location, minimal ablation margin, RAS mutation status, prior hepatectomy, and extrahepatic disease. Further understanding of the impact of tumor biology and advanced imaging guidance on overall patient outcomes might help to tailor its application, and improve outcomes of image-guided ablation.

Minimally invasive image-guided therapy of primary and metastatic pancreatic cancer

Pancreatic cancer is a challenging malignancy with limited treatment options and poor life expectancy. The only curative option is surgical resection, but only 15%-20% of patients are resectable at presentation because more than 50% of patients has distant metastasis at diagnosis and the rest of them has locally advanced pancreatic cancer (LAPC). The standard of care first line treatment for LAPC patients is chemotherapy with or without radiation therapy. Recent developments in minimally invasive ablative techniques may add to the treatment armamentarium of LAPC. There are increasing number of studies evaluating these novel ablative techniques, including radiofrequency ablation, microwave ablation, cryoablation and irreversible electroporation. Most studies which included pancreatic tumor ablation, demonstrated improved overall survival in LAPC patients. However, the exact protocols are yet to set up to which stage of the treatment algorithm ablative techniques can be added and in what kind of treatment combinations. Patients with metastatic pancreatic cancer has dismal prognosis with 5-year survival is only 3%. The most common metastatic site is the liver as 90% of pancreatic cancer patients develop liver metastasis. Chemotherapy is the primary treatment option for patients with metastatic pancreatic cancer. However, when the tumor is not responding to chemotherapy or severe drug toxicity develops, locoregional liver-directed therapies can provide an opportunity to control intrahepatic disease progression and improve survival in selected patients. During the last decade new therapeutic options arose with the advancement of minimally invasive technologies to treat pancreatic cancer patients. These new therapies have been a topic of increasing interest due to the severe prognostic implications of locally advanced and metastatic pancreatic cancer and the low comorbid risk of these procedures. This review summarizes new ablative options for patients with LAPC and percutaneous liver-directed therapies for patients with liver-dominant metastatic disease.

Comparison of procedure-related complications between percutaneous cryoablation and radiofrequency ablation for treating periductal hepatocellular carcinoma

PURPOSE

This study aimed to evaluate the incidence and severity of biliary complications after treating periductal hepatocellular carcinomas (HCCs) using either cryoablation (CA) or radiofrequency ablation (RFA) and assess independent risk factors for biliary complications after treatment.

MATERIALS AND METHODS

Between July 2008 and August 2018, 949 patients with treatment-naïve HCCs underwent either RFA or CA in our institution. Of these, patients with multiple HCCs, tumors equal to or larger than 3 cm or smaller than 1 cm, and tumors with non-periductal locations were excluded. Finally, 31 patients and 25 patients were included in the RFA group and the CA group, respectively. The incidence and severity of biliary complications were compared between the RFA and CA groups. The risk factors for biliary complications were assessed using univariable and multivariable logistic regression analyses using the following variables: age, sex, tumor size, Child-Pugh score, tumor location (peripheral duct versus central duct), ablation method (RFA versus CA), the number of applicators, ablation time, and ablation volume.

RESULTS

The incidence and severity of biliary complications were significantly higher in the RFA group than in the CA group (p = 0.007 and p = 0.002, respectively). In univariable and multivariable analyses, the ablation method was an independent risk factor for biliary complications (p = 0.004 and 0.013, respectively).

CONCLUSIONS

The incidence and severity of biliary complications after treating HCCs abutting the bile duct are lower in CA than RFA, demonstrating that CA is safer than RFA for ablating small periductal HCCs.

Stereotactic Percutaneous Electrochemotherapy as Primary Approach for Unresectable Large HCC at the Hepatic Hilum

Electrochemotherapy (ECT) is a novel non-thermal ablative technique that combines chemotherapy and the application of electric pulses for reversible cell membrane electroporation. This method was recently performed in the treatment of deep-seated liver tumors during open surgery but experience about percutaneous ECT is rare and further developments like combination of percutaneous ECT with stereotactic navigated devices may be very promising. We report on a case of a 4.7 × 4.5 × 3.5 cm unresectable HCC at the hepatic hilum adjacent to the major vessels and the bile duct that was successfully treated using percutaneous ECT in combination with stereotactic navigation. Follow-up imaging 6 weeks and 6 months after ECT showed complete response.

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.

Gemcitabine plus concurrent irreversible electroporation vs gemcitabine alone for locally advanced pancreatic cancer

BACKGROUND

Locally advanced pancreatic cancer (LAPC) is a common malignant digestive system tumor that ranks as the fourth leading cause of cancer-related death in the world. The prognosis of LAPC is poor even after standard treatment. Irreversible electroporation (IRE) is a novel ablative strategy for LAPC. Several studies have confirmed the safety of IRE. To date, no prospective studies have been performed to investigate the therapeutic efficacy of conventional gemcitabine (GEM) plus concurrent IRE.

AIM

To compare the therapeutic efficacy between conventional GEM plus concurrent IRE and GEM alone for LAPC.

METHODS

From February 2016 to September 2017, a total of 68 LAPC patients were treated with GEM plus concurrent IRE n = 33) or GEM alone n = 35). Overall survival (OS), progression free survival (PFS), and procedure-related complications were compared between the two groups. Multivariate analyses were performed to identify any prognostic factors.

RESULTS

There were no treatment-related deaths. The technical success rate of IRE ablation was 100%. The GEM + IRE group had a significantly longer OS from the time of diagnosis of LAPC (19.8 mo vs 9.3 mo, P < 0.0001) than the GEM alone group. The GEM + IRE group had a significantly longer PFS (8.3 mo vs 4.7 mo, P < 0.0001) than the GEM alone group. Tumor volume less than 37 cm3 and GEM plus concurrent IRE were identified as significant favorable factors for both the OS and PFS.

CONCLUSION

Gemcitabine plus concurrent IRE is an effective treatment for patients with LAPC.

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 Hepatic Tumors: Protocol Standardization Using the Modified Delphi Technique

PURPOSE

A consensus study of panelists was performed to provide a uniform protocol regarding (contra) indications, procedural parameters, perioperative care, and follow-up of irreversible electroporation (IRE) for the treatment of hepatic malignancies.

MATERIALS AND METHODS

Interventional radiologists who had 2 or more publications on IRE, reporting at least 1 patient cohort in the field of hepatobiliary IRE, were recruited. The 8 panelists were asked to anonymously complete 3 iterative rounds of IRE-focused questionnaires to collect data according to a modified Delphi technique. Consensus was defined as having reached 80% or greater agreement.

RESULTS

Panel members' response rates were 88%, 75%, and 88% in rounds 1, 2, and 3, respectively; consensus was reached on 124 of 136 items (91%). Percutaneous or intraoperative hepatic IRE should be considered for unresectable primary and secondary malignancies that are truly unsuitable for thermal ablation because of proximity to critical structures. Absolute contraindications are ventricular arrhythmias, cardiac stimulation devices, and congestive heart failure of New York Heart Association class 3 or higher. A metal stent outside the ablation zone should not be considered a contraindication. For the only commercially available IRE device, the recommended settings are an inter-electrode distance of 10-20 mm and an exposure length of 20 mm. After 10 test pulses, 90 treatment pulses of 1500 V/cm should be delivered continuously, with a pulse length of 70-90 μs. The first post-procedural follow-up should take place 1 month after IRE and thereafter every 3 months, using cross-sectional imaging plus tumor marker assessment.

CONCLUSIONS

This article provides recommendations, created by a modified Delphi consensus study, regarding patient selection, workup, procedure, and follow-up of IRE treatment for hepatic malignancies.

Effectiveness and safety of irreversible electroporation for recurrent hepatocellular carcinoma ineligible for thermal ablation after surgery

Objectives

To preliminarily evaluate the clinical effectiveness and safety of computed tomography (CT) image-guided irreversible electroporation (IRE) for the treatment of recurrent hepatocellular carcinoma (HCC) after surgical resection.

Methods

From January 2016 to February 2018, 18 patients diagnosed with recurrent HCC after surgical resection received IRE under CT image guidance for 22 tumors. Patients were enrolled for IRE when ineligible for thermal ablation due to tumor location. Clinical records and imaging data were reviewed to assess complete ablation rate, local tumor progression free rate (LTPFR), local tumor progression free survival (LTPFS) and complications after a median follow-up time of 14 months.

Results

Successful complete ablations were achieved in 20/22 (90.1%) tumors. Mean LTPFS was 10.5 ​± ​9.4 months. Overall 3-, 6- and 12-months LTPFR in 22 tumors following IRE were 68.2% (95% confidence interval [CI]: 45%–83%), 59.1% (95% CI: 33%–76%) and 36.4% (95% CI: 17%–56%), respectively. Complications included pneumothorax (2/18, 11.1%), localized pain (3/18, 16.7%), bile duct dilation (1/18, 5.6%) and transient hypertension (1/18, 5.6%). No major complications or treatment-related deaths were observed. The alpha-fetoprotein levels of two patients decreased to the normal range at 3 and 4 months, respectively.

Conclusions

This study showed that percutaneous CT image-guided IRE can serve as a safe and effective treatment for recurrent HCC not suitable for thermal ablation.

Transchondral access for irreversible electroporation of hepatocellular carcinoma

Ablative treatment for hepatocellular carcinoma is standard of care in selected settings and is endorsed by international societal guidelines. Centrally located hepatocellular carcinoma are difficult to treat due to their proximity to vasculature and central bile ducts. Irreversible electroporation is a nonthermal ablation modality that has been shown to preserve the extracellular matrix and is less likely to damage structures such as bile ducts and is not susceptible to vascular heat sink. Successful irreversible electroporation requires the parallel placement of probes which can be prevented by ribs or the sternum. This case report describes the use of the coaxial bone biopsy system to enable transchondral access and facilitate parallel placement of probes during irreversible electroporation IRE for the treatment of hepatocellular carcinoma.

High-Voltage Electrical Pulses in Oncology: Irreversible Electroporation, Electrochemotherapy, Gene Electrotransfer, Electrofusion, and Electroimmunotherapy

This review summarizes the use of high-voltage electrical pulses (HVEPs) in clinical oncology to treat solid tumors with irreversible electroporation (IRE) and electrochemotherapy (ECT). HVEPs increase the membrane permeability of cells, a phenomenon known as electroporation. Unlike alternative ablative therapies, electroporation does not affect the structural integrity of surrounding tissue, thereby enabling tumors in the vicinity of vital structures to be treated. IRE uses HVEPs to cause cell death by inducing membrane disruption, and it is primarily used as a radical ablative therapy in the treatment of soft-tissue tumors in the liver, kidney, prostate, and pancreas. ECT uses HVEPs to transiently increase membrane permeability, enhancing cellular cytotoxic drug uptake in tumors. IRE and ECT show immunogenic effects that could be augmented when combined with immunomodulatory drugs, a combination therapy the authors term electroimmunotherapy. Additional electroporation-based technologies that may reach clinical importance, such as gene electrotransfer, electrofusion, and electroimmunotherapy, are concisely reviewed. HVEPs represent a substantial advancement in cancer research, and continued improvement and implementation of these presented technologies will require close collaboration between engineers, interventional radiologists, medical oncologists, and immuno-oncologists.

Irreversible Electroporation: Background, Theory, and Review of Recent Developments in Clinical Oncology

Irreversible electroporation (IRE) has established a clinical niche as an alternative to thermal ablation for the eradication of unresectable tumors, particularly those near critical vascular structures. IRE has been used in over 50 independent clinical trials and has shown clinical success when used as a standalone treatment and as a single component within combinatorial treatment paradigms. Recently, many studies evaluating IRE in larger patient cohorts and alongside other novel therapies have been reported. Here, we present the basic principles of reversible electroporation and IRE followed by a review of preclinical and clinical data with a focus on tumors in three organ systems in which IRE has shown great promise: the prostate, pancreas, and liver. Finally, we discuss alternative and future developments, which will likely further advance the use of IRE in the clinic.

Individualized Ablation of Hepatocellular Carcinoma: Tailored Approaches across the Phenotype Spectrum

Ablation is now recommended by international guidelines for the definitive treatment of hepatocellular carcinoma (HCC). Extensive clinical studies have demonstrated outcomes comparable to surgical resection with shorter hospital stays, decreased costs, and improved quality of life. Successful ablation requires complete treatment of both tumor and margin while preserving critical adjacent structures. HCC exhibits highly variable presentations in both anatomic involvement and biology which have significant implications on choice of ablative therapy. There are now abundant ablation modalities and adjunctive techniques which can be used to individualize ablation and maximize curative results. This article provides a patient-centered summary of approaches to HCC ablation in the context of patient performance, hepatic reserve, tumor phenotype and biology, intra- and extrahepatic anatomy, and ablation technology.

Ablation of Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma is the second most common primary liver cancer but represents only a small portion of all primary liver cancers. At the time of diagnosis, patients are often not surgical candidates due to tumor burden of other comorbidities. In addition, there is a very high rate of tumor recurrence after resection. Local regional therapies, specifically ablative therapies of radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation, have proven to be beneficial with other hepatic tumors. The purpose of this review is to provide an overview and update of the medical literature demonstrating ablative therapy as a treatment option for intrahepatic cholangiocarcinoma.

Locoregional Therapy, Immunotherapy and the Combination in Hepatocellular Carcinoma: Future Directions

Image-guided locoregional therapies (LRTs) have long been a vital part of treatment regimens for hepatocellular carcinoma (HCC). Ablation, chemoembolization, and radioembolization are examples of commonly used treatment techniques for HCC. This review describes the various methods utilized to treat HCC in the field of interventional oncology and also focuses on new and novel treatment concepts being developed in the field including the use of novel immunotherapy agents and combination therapy of LRTs with immunotherapy.

Peri-tumoral Metallic Implants Reduce the Efficacy of Irreversible Electroporation for the Ablation of Colorectal Liver Metastases

PURPOSE

To evaluate the effect of peri-tumoral metallic implants (MI) on the safety and efficacy of percutaneous irreversible electroporation (IRE) of colorectal liver metastasis (CRLM).

MATERIALS AND METHODS

In this retrospective study, 25 patients (12 women, 13 men; MI: 13, no MI: 12) were treated for 29 CRLM. Patient characteristics, tumor location and size, treatment parameters and the presence of MI were evaluated as determinants of local tumor progression (LTP) with the competing risks model (univariate and multivariate analyses). Patient-specific computer models were created to examine the effect of the MI on the electric field used to induce IRE, probability of cell kill and potential thermal effects.

RESULTS

Patients had a median follow-up of 25 months, during which no IRE-related major complications were reported. Univariate analysis showed that tumor size (> 2 cm), probe spacing (> 20 mm) and the presence of MI (p < 0.05) were significant predictors of time to LTP, but only the latter was found to be an independent predictor on multivariate analysis (sub-hazard ratio = 6.5; [95% CI 1.99, 21.4]; p = 0.002). The absence of peri-tumoral MI was associated with higher progression-free survival at 12 months (92.3% [56.6, 98.9] vs 12.5% [2.1, 32.8]). Computer simulations indicated significant distortions and reduction in electric field strength near MI, which could have contributed to under-treatment of the tumor.

CONCLUSIONS

Peri-tumoral MI increases the risk of treatment failure following IRE of CRLM.

Percutaneous Laser Ablation of Hepatic Tumors Located in the Portacaval Space: Preliminary Results

BACKGROUND AND OBJECTIVES

Limited data have been used to evaluate the feasibility and effectiveness of percutaneous laser ablation (PLA) (a modality that has been proven to be a safe method for tumors in high-risk locations) for hepatic tumors in the space between the portal vein and inferior vena cava (IVC). The goal of this study was to investigate the characteristics and therapeutic effectiveness of ultrasound-guided PLA of hepatic tumors in the portacaval space.

STUDY DESIGN/MATERIALS AND METHODS

Ten patients, who had hepatic tumors in the portacaval space (defined as tumors located in the space formed by the hepatic portal vein and IVC less than 5 mm from the margins of both vessels), receiving ultrasound-guided PLA between January 2016 and June 2017 were analyzed. Tumors in the type I portacaval space were enclosed on three sides of major vessels, and tumors in the type II portacaval space were enclosed on two sides of major vessels. The technical success, treatment response, complete tumor ablation (CTA), local tumor progression (LTP), and distant tumor recurrence (DTR) were assessed and recorded at the follow-up.

RESULTS

The mean tumor diameter was 1.8 ± 0.4 cm. Technical success and initial CTA were achieved in all 10 patients without major complications. The 6-month and 12-month LTP rates were 0% and 10%, respectively. The DTR rate was 20% at both the 6- and 12-month follow-ups.

CONCLUSIONS

The preliminary results showed that ultrasound-guided PLA was feasible and safe for tumors in the portacaval space, and further studies on larger populations with a longer follow-up are needed to delineate the use of PLA and evaluate its therapeutic efficacy. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

A Conceivable Mechanism Responsible for the Synergy of High and Low Voltage Irreversible Electroporation Pulses

Irreversible electroporation (IRE), is a new non-thermal tissue ablation technology in which brief high electric field pulses are delivered across the target tissue to induce cell death by irreversible permeabilization of the cell membrane. A deficiency of conventional IRE is that the ablation zone is relatively small, bounded by the irreversible electroporation isoelectric field margin. In the previous studies we have introduced a new treatment protocol that combines few short high voltage (SHV) pulses with long low-voltage (LLV) pulses. In the previous studies, we also have shown that the addition of few SHV pulses increases by almost a factor of two the area ablated by a protocol that employs only the LLV pulses. This study employs potato and gel phantom to generate a plausible explanation for the mechanism. The study provides circumstantial evidence that the mechanism involved is the production of electrolytic compounds by the LLV pulse sequence, which causes tissue ablation beyond the margin of the irreversible electroporation isoelectric field generated by the SHV pulses, presumable to the reversible electroporation isoelectric field margin generated by the SHV pulses.

Is irreversible electroporation safe and effective in the treatment of hepatobiliary and pancreatic cancers?

BACKGROUND

Irreversible electroporation (IRE) is a novel ablative technique for hepatobiliary and pancreatic cancers. This review summarizes the data regarding the safety and efficacy of IRE in the treatment of hepatobiliary and pancreatic cancers.

DATA SOURCES

Studies were identified by searching PubMed and Embase for articles published in English from database inception through July 31, 2017. For inclusion, each clinical study had to report morbidity and survival data on hepatobiliary and pancreatic cancers treated with IRE and contain at least 10 patients. Studies that met these criteria were included for analysis. Two authors assessed each clinical study for data extraction. The controversial parts were resolved through discussion with seniors.

RESULTS

A total of 24 clinical studies were included. Fourteen focused on hepatic ablation with IRE comprising 437 patients with 666 lesions of different tumor types. Two patients (0.5%) died after the IRE procedure. Morbidity of hepatic ablation with IRE ranged from 7% to 35%. Most complications were mild. Complete response for hepatic tumors was reported as 57%-97%. Ten studies with 455 patients focused on pancreatic IRE. The overall mortality of IRE in pancreatic cancer was 2%. Overall severe morbidity of IRE in pancreatic cancer ranged from 0 to 20%. The median overall survival after IRE ranged from 7 to 23 months. Patients treated with IRE combined with surgical resection showed a longer overall survival.

CONCLUSIONS

IRE significantly improves the prognosis of advanced hepatobiliary and pancreatic malignances, and companied with less complications. Hence, IRE is a relatively safe and effective non-thermal ablation strategy and potentially recommended as an option for therapy of patients with hepatobiliary and pancreatic malignances.

Current State of Tumor Ablation Therapies

The most common primary liver malignancy, hepatocellular carcinoma (HCC), has a high likelihood of mortality, and much effort into early detection and treatment has occurred. Multiple staging systems have surfaced of which some guide treatment. Curative intent is a goal of early-staged HCC treatment, and this can be achieved with surgical resection, liver transplantation, and minimally invasive percutaneous therapies such as tumor ablation. Many of the newer ablation techniques have evolved from shortcomings of prior methods which have resulted in an expanded number of applications for tumor ablation. Our review focuses on current mainstream image-guided percutaneous ablation modalities which are commonly performed as an alternative to surgery.

Irreversible Electroporation for Unresectable Hepatocellular Carcinoma: Initial Experience

PURPOSE

To evaluate the efficacy and safety of irreversible electroporation (IRE) in the treatment of unresectable hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A retrospective study was conducted from September 2014 to June 2017. A total of 21 HCCs in 21 patients with cirrhosis were treated with IRE. There were eight subcapsular or exophytic, ten perivascular and three peribiliary tumors. The median tumor size was 26 mm (range 14-40 mm). The technical success of the procedure was recorded. Median follow-up, median time to local recurrence, median local tumor progression-free survival (PFS) and complications were recorded.

RESULTS

Technical success was achieved in all the patients. The median follow-up was 10 months (range 2-30 months). The median time to local recurrence and local tumor PFS were 4 months (range 3-4 months) and 7 months (range 3-30 months), respectively. The tumor-related factor that was significantly associated with local PFS was the size. Maximum tumor diameter < 25 mm was significantly associated with local tumor PFS (p = 0.045). Other parameters including tumor location, segmental portal vein thrombosis, baseline alpha-fetoprotein level and underlying etiology did not affect local tumor PFS. Complications were noted in nine patients and were classified as grades 1 and 2. No procedure-related mortality was encountered.

CONCLUSION

IRE is an effective treatment for ablation of small HCCs. Larger prospective studies with strict selection criteria will establish the safety and efficacy of IRE in the treatment of unresectable HCC in patients who cannot undergo thermal ablation.