Ablation therapy for hepatocellular carcinoma: past, present and future perspectives

Embolic and Ablative Therapy for Hepatocellular Carcinoma

Embolic and ablative locoregional therapies (LRTs) for hepatocellular carcinoma are widely used to cure, bridge, or downstage patients for more definitive therapies. Common ablative therapies include microwave ablation and radiofrequency ablation, while embolic options include transarterial chemoembolization and 90Y transarterial radioembolization. While these therapies can be highly effective for the appropriate stage of disease, LRTs can suffer from a high rate of posttreatment recurrences. Considerations for administration of specific therapies include disease burden and underlying liver function. Recent data on concomitant or adjuvant systemic therapy, with LRT, have the potential to improve disease control and improve outcomes in this high-risk patient population.

Racial/Ethnic Disparities and Immunotherapeutic Advances in the Treatment of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) remains one of the leading causes of death among many associated liver diseases. Various conventional strategies have been utilized for treatment, ranging from invasive surgeries and liver transplants to radiation therapy, but fail due to advanced disease progression, late screening/staging, and the various etiologies of HCC. This is especially evident within racially distinct populations, where incidence rates are higher and treatment outcomes are worse for racial/ethnic minorities than their Caucasian counterparts. However, with the rapid development of genetic engineering and molecular and synthetic biology, many novel strategies have presented promising results and have provided potential treatment options. In this review, we summarize past treatments, how they have shaped current treatments, and potential treatment strategies for HCC that may prove more effective in the future.

Harnessing the Electrochemical Effects of Electroporation-Based Therapies to Enhance Anti-tumor Immune Responses

This study introduces a new method of targeting acidosis (low pH) within the tumor microenvironment (TME) through the use of cathodic electrochemical reactions (CER). Low pH is oncogenic by supporting immunosuppression. Electrochemical reactions create local pH effects when a current passes through an electrolytic substrate such as biological tissue. Electrolysis has been used with electroporation (destabilization of the lipid bilayer via an applied electric potential) to increase cell death areas. However, the regulated increase of pH through only the cathode electrode has been ignored as a possible method to alleviate TME acidosis, which could provide substantial immunotherapeutic benefits. Here, we show through ex vivo modeling that CERs can intentionally elevate pH to an anti-tumor level and that increased alkalinity promotes activation of naïve macrophages. This study shows the potential of CERs to improve acidity within the TME and that it has the potential to be paired with existing electric field-based cancer therapies or as a stand-alone therapy.

Role of CD147 in the development and diagnosis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, and the third leading cause of cancer-related deaths worldwide. HCC is characterized by insidious onset, and most patients are diagnosed at an advanced stage with a poor prognosis. Identification of biomarkers for HCC onset and progression is imperative to development of effective diagnostic and therapeutic strategies. CD147 is a glycoprotein that is involved in tumor cell invasion, metastasis and angiogenesis through multiple mechanisms. In this review, we describe the molecular structure of CD147 and its role in regulating HCC invasion, metastasis and angiogenesis. We highlight its potential as a diagnostic and therapeutic target for HCC.

Modeling of a single bipolar electrode with tines for irreversible electroporation delivery

Irreversible electroporation (IRE) is a non-thermal tumor ablation technology employed to treat solid tumors not amenable to resection or thermal ablation. The IRE systems currently in clinical use deliver electrical pulses via multiple monopolar electrodes. This approach can present significant technical challenges due to the requirement for accurate placement of multiple electrodes and maintenance of parallel electrode alignment during pulse delivery. In this study, we sought to evaluate a novel IRE electrode configuration consisting of a single bipolar electrode with deployable tines. Using commercial finite element software predicted ablation outcomes, thermal damage, ablation sphericity, and energy delivery were calculated for existing monopolar and bipolar electrodes, and bipolar electrodes with either 4 or 8 deployable tines. The bipolar electrodes with tines generated larger predicted ablations compared to existing monopolar (>100%) and bipolar (>10%) arrangements, and the ablation shape using bipolar electrodes with tines were more spherical than those modeled for bipolar electrodes. Thermal damage modeled for bipolar electrodes and bipolar electrodes with tines was less than that of monopolar electrodes (using identical pulse parameters), and bipolar electrodes with tines delivered less energy than monopolar or bipolar electrodes. These studies using a single point of device insertion suggest the potential for developing alternative IRE delivery techniques, and may simplify clinical use and increase the predicted ablation shape/volume.

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.

Simplified Non-Thermal Tissue Ablation With a Single Insertion Device Enabled by Bipolar High-Frequency Pulses

OBJECTIVE

To demonstrate the feasibility of a single electrode and grounding pad approach for delivering high frequency irreversible electroporation treatments (H-FIRE) in in-vivo hepatic tissue.

METHODS

Ablations were created in porcine liver under surgical anesthesia by adminstereing high frequency bursts of 0.5-5.0 μs pulses with amplitudes between 1.1-1.7 kV in the absence of cardiac synchronization or intraoperative paralytics. Finite element simulations were used to determine the electric field strength associated with the ablation margins (E_Lethal) and predict the ablations feasible with next generation electronics.

RESULTS

All animals survived the procedures for the protocol duration without adverse events. E_Lethal of 2550, 1650, and 875 V/cm were found for treatments consisting of 100x bursts containing 0.5 μs pulses and 25, 50, and 75 μs of energized-time per burst, respectively. Treatments with 1 μs pulses consisting of 100 bursts with 100 μs energized-time per burst resulted in E_Lethal of 650 V/cm.

CONCLUSION

A single electrode and grounding pad approach was successfully used to create ablations in hepatic tissue. This technique has the potential to reduce challenges associated with placing multiple electrodes in anatomically challenging environments.

SIGNIFICANCE

H-FIRE is an in situ tumor ablation approach in which electrodes are placed within or around a targeted region to deliver high voltage electrical pulses. Electric fields generated around the electrodes induce irrecoverable cell membrane damage leading to predictable cell death in the relative absence of thermal damage. The sparing of architectural integrity means H-FIRE offers potential advantages compared to thermal ablation modalities for ablating tumors near critical structures.

A novel 3-dimensional electromagnetic guidance system increases intraoperative microwave antenna placement accuracy

BACKGROUND

Failure to locate lesions and accurately place microwave antennas can lead to incomplete tumor ablation. The Emprint™ SX Ablation Platform employs real-time 3D-electromagnetic spatial antenna tracking to generate intraoperative laparoscopic antenna guidance. We sought to determine whether Emprint™ SX affected time/accuracy of antenna-placement in a laparoscopic training model.

METHODS

Targets (7-10 mm) were set in agar within a laparoscopic training device. Novices (no surgical experience), intermediates (surgical residents), and experts (HPB-surgeons) were asked to locate and hit targets using a MWA antenna (10-ultrasound only, 10-Emprint™ SX). Time to locate target, number of attempts to hit the target, first-time hit rate, and time from initiating antenna advance to hitting the target were measured.

RESULTS

Participants located 100% of targets using ultrasound, with experts taking significantly less time than novices and intermediates. Using ultrasound only, successful hit-rates were 70% for novices and 90% for intermediates and experts. Using Emprint™ SX, successful hit rates for all 3-groups were 100%, with significantly increased first-time hit-rates and reduced time required to hit targets compared to ultrasound only.

DISCUSSION

Emprint™ SX significantly improved accuracy and speed of antenna-placement independent of experience, and was particularly beneficial for novice users.

High-Frequency Irreversible Electroporation: Safety and Efficacy of Next-Generation Irreversible Electroporation Adjacent to Critical Hepatic Structures

Irreversible electroporation (IRE) is a nonthermal ablation modality employed to induce in situ tissue-cell death. This study sought to evaluate the efficacy of a novel high-frequency IRE (H-FIRE) system to perform hepatic ablations across, or adjacent to, critical vascular and biliary structures. Using ultrasound guidance H-FIRE electrodes were placed across, or adjacent to, portal pedicels, hepatic veins, or the gall bladder in a porcine model. H-FIRE pulses were delivered (2250 V, 2-5-2 pulse configuration) in the absence of cardiac synchronization or intraoperative paralytics. Six hours after H-FIRE the liver was resected and analyzed. Nine ablations were performed in 3 separate experimental groups (major vessels straddled by electrodes, electrodes placed adjacent to major vessels, electrodes placed adjacent to gall bladder). Average ablation time was 290 ± 63 seconds. No electrocardiogram abnormalities or changes in vital signs were observed during H-FIRE. At necropsy, no vascular damage, coagulated-thermally desiccated blood vessels, or perforated biliary structures were noted. Histologically, H-FIRE demonstrated effective tissue ablation and uniform induction of apoptotic cell death in the parenchyma independent of vascular or biliary structure location. Detailed microscopic analysis revealed minor endothelial damage within areas subjected to H-FIRE, particularly in regions proximal to electrode insertion. These data indicate H-FIRE is a novel means to perform rapid, reproducible IRE in liver tissue while preserving gross vascular/biliary architecture. These characteristics raise the potential for long-term survival studies to test the viability of this technology toward clinical use to target tumors not amenable to thermal ablation or resection.

Induction of rapid, reproducible hepatic ablations using next-generation, high frequency irreversible electroporation (H-FIRE) in vivo

INTRODUCTION

Irreversible electroporation (IRE) offers an alternative to thermal tissue ablation in situ. High-frequency IRE (H-FIRE), employing ultra-short bipolar electrical pulses, may overcome limitations associated with existing IRE technology to create rapid, reproducible liver ablations in vivo.

METHODS

IRE electrodes (1.5 cm spacing) were inserted into the hepatic parenchyma of swine (n = 3) under surgical anesthesia. In the absence of paralytics or cardiac synchronization five independent H-FIRE ablations were performed per liver using 100, 200, or 300 pulses (2250 V, 2-5-2 μs configuration). Animals were maintained under isoflurane anesthesia for 6 h prior to analysis of ablation size, reproducibility, and apoptotic cell death.

RESULTS

Mean ablation time was 230 ± 31 s and no EKG abnormalities occurred during H-FIRE. In 1/15 HFIRE's minor muscle twitch (rectus abdominis) was recorded. Necropsy revealed reproducible ablation areas (34 ± 4 mm(2), 88 ± 11 mm(2) and 110 ± 11 mm(2); 100-, 200- and 300-pulses respectively). Tissue damage was predominantly apoptotic at pulse delivery ≤200 pulses, after which increasing evidence of tissue necrosis was observed.

CONCLUSION

H-FIRE can be used to induce rapid, predictable ablations in hepatic tissue without the need for intraoperative paralytics or cardiac synchronization. These advantages may overcome limitations that restrict currently available IRE technology for hepatic ablations.

Role of alcohol in the development and progression of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a significant cause of cancer-related morbidity and mortality. Chronic, heavy ethanol consumption is a major risk for developing the worsening liver pathologies that culminate in hepatic cirrhosis, the leading risk factor for developing HCC. A significant body of work reports the biochemical and pathological consequences of ethanol consumption and metabolism during hepatocarcinogeneis. The systemic effects of ethanol means organ system interactions are equally important in understanding the initiation and progression of HCC within the alcoholic liver. This review aims to summarize the effects of ethanol-ethanol metabolism during the pathogenesis of alcoholic liver disease, the progression toward HCC and the importance of ethanol as a comorbid factor for HCC development.

Optimal Ablation Volumes Are Achieved at Submaximal Power Settings in a 2.45-GHz Microwave Ablation System

Introduction. Local ablative therapies, including microwave ablation (MWA), are common treatment modalities for in situ tumor destruction. Currently, 2.45-GHz ablation systems are gaining prominence because of the shorter application times required. The aims of this study were to determine optimal power and time to ablation volume (AbV) ratios for a new 1.8-mm–2.45-GHz antenna using ex vivo tissue models. Methods. The 1.8-mm–2.45-GHz Accu2i MWA system was employed to perform ablations in bovine liver, porcine muscle, and porcine kidney ex vivo. Whole tissues were prewarmed (35°C) and multiple ablations performed at power settings of 60 to 180 W for 2- to 6-minute time intervals. Postablation, tissues were dissected, AbVs calculated, and correlations to power and time settings made. Results. Significant increases in AbV were measured between each of the time points for a constant power setting in all 3 tissues. Increasing power settings led to significant increases in AbV at power settings ≤140 W. However, no significant increase in AbV was obtained at power settings >140 W. Conclusions. Optimal efficiency for MWA using a new 1.8-mm–2.45-GHz system is achieved at settings of ≤140 W for 6 minutes in a range of ex vivo tissue and no additional benefit occurs by increasing the power setting to 180 W in these tissues.

Survival analysis of patients with stage I and II hepatocellular carcinoma after a liver transplantation or liver resection

INTRODUCTION

Liver transplantation (LT) is a treatment option in select patients with hepatocellular carcinoma (HCC). The aim of the present study was to compare survival in Stage I or II HCC patients undergoing either liver transplant (LT) or a liver resection (LR).

METHOD

The study is a retrospective analysis of the National Cancer Data Base (1998-2011). In total, 148,882 patients with liver cancer were identified, of which 5-year survival data (1998-2006) were available for 64,227 patients. Patients were stratified by the American Joint Committee on Cancer (AJCC) clinical stage I and II. Kaplan-Meier curves and log-rank tests were used for statistical analysis.

RESULTS

3340 HCC patients met analysis criteria. Among stage I HCC, 860 had LT and 871 had LR. Among stage II HCC, 833 had LT and 776 LR. In stage I patients the median survival for LT and LR were 127.9 and 56.7 months, respectively, (P < 0.0001) and in stage II patients the median survival was 110.8 and 42.8 months (P < 0.0001). Unlike LT patients, LR patients with Stage I HCC had a longer median survival compared with Stage II patients (P = 0.0002).

CONCLUSION

Liver transplantation offers a survival advantage compared with a liver resection among patients with Stage I and II HCC. LT is the best surgical treatment for early stage (I/II) HCC in patients with advanced fibrosis or cirrhosis, whereas LR provides equivalent outcomes to LT in patients without advanced fibrosis and should be considered as the first surgical option.