Intrahepatic radiofrequency ablation versus electrochemical treatment in vivo

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.

Advances of Electroporation-Related Therapies and the Synergy with Immunotherapy in Cancer Treatment

Electroporation is the process of instantaneously increasing the permeability of a cell membrane under a pulsed electric field. Depending on the parameters of the electric pulses and the target cell electrophysiological characteristics, electroporation can be either reversible or irreversible. Reversible electroporation facilitates the delivery of functional genetic materials or drugs to target cells, inducing cell death by apoptosis, mitotic catastrophe, or pseudoapoptosis; irreversible electroporation is an ablative technology which directly ablates a large amount of tissue without causing harmful thermal effects; electrotherapy using an electric field can induce cell apoptosis without any aggressive invasion. Reversible and irreversible electroporation can also activate systemic antitumor immune response and enhance the efficacy of immunotherapy. In this review, we discuss recent progress related to electroporation, and summarize its latest applications. Further, we discuss the synergistic effects of electroporation-related therapies and immunotherapy. We also propose perspectives for further investigating electroporation and immunotherapy in cancer treatment.

An Ultrasonically Powered Implantable Microprobe for Electrolytic Ablation

Electrolytic ablation (EA) is a promising nonthermal tumor ablation technique that destroys malignant cells through induction of a locoregional pH change. EA is typically performed by inserting needle electrodes inside the tumor followed by application of direct current (DC), thus inducing electrolysis and creating localized pH changes around the electrodes. In this paper, we report an ultrasonically powered implantable EA microprobe that may increase the clinical relevance of EA by allowing wireless control over device operation (capability to remotely turn the device on and off) and providing flexibility in treatment options (easier to administer fractionated doses over a longer period). The wireless EA microprobe consists of a millimeter-sized piezoelectric ultrasonic receiver, a rectifier circuit, and a pair of platinum electrodes (overall size is 9 × 3 × 2 mm³). Once implanted through a minimally invasive procedure, the microprobe can stay within a solid tumor and be repeatedly used as needed. Ultrasonic power allows for efficient power delivery to mm-scale devices implanted deep within soft tissues of the body. The microprobe is capable of producing a direct current of 90 µA at a voltage of 5 V across the electrodes under low-intensity ultrasound (~200 mW/cm²). The DC power creates acidic (pH < 2) and alkaline (pH > 12.9) regions around the anode and the cathode, respectively. The pH change, measured using tissue-mimicking agarose gel, extends to 0.8 cm³ in volume within an hour at an expansion rate of 0.5 mm³/min. The microprobe-mediated EA ablative capability is demonstrated in vitro in cancer cells and ex vivo in mouse liver.

MR Imaging Enables Real-Time Monitoring of In Vitro Electrolytic Ablation of Hepatocellular Carcinoma

PURPOSE

To evaluate the capability of T2-weighted magnetic resonance (MR) imaging to monitor electrolytic ablation-induced cell death in real time.

MATERIALS AND METHODS

Agarose phantoms arranged as an electrolytic cell were exposed to varying quantities of electric charge under constant current to create a pH series. The pH phantoms were subjected to T2-weighted imaging with region of interest quantitation of the acquired signal intensity. Subsequently, hepatocellular carcinoma (HCC) cells encapsulated in an agarose gel matrix were subjected to 10 V of electrolytic ablation for variable lengths of time with and without concurrent T2-weighted MR imaging. Cellular death was confirmed by a fluorescent reporter. Finally, to confirm that real-time MR images corresponded to ablation zones, 10 V electrolytic ablations were performed followed by the addition of pH-neutralizing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer.

RESULTS

Analysis of MR imaging from agarose gel pH phantoms demonstrated a relationship between signal intensity and pH at the anodes and cathodes. The steep negative phase of the anode model (pH < 3.55) and global minimum of the cathode model (pH ≈ 11.62) closely approximated established cytotoxic pH levels. T2-weighted MR imaging demonstrated a strong correlation of ablation zones with regions of HCC cell death (r = 0.986; R² = 0.916; P < .0001). The addition of HEPES buffer to the hydrogel resulted in complete obliteration of MR imaging-observed ablation zones, confirming that change in pH directly caused the observed signal intensity attenuation of the ablation zone.

CONCLUSIONS

T2-weighted MR imaging enabled the real-time detection of electrolytic ablation zones, demonstrating a strong correlation with histologic cell death.

Electrochemotherapy - Emerging applications technical advances, new indications, combined approaches, and multi-institutional collaboration

The treatment of tumors with electrochemotherapy (ECT) has surged over the past decade. Thanks to the transient cell membrane permeabilization induced by the short electric pulses used by ECT, cancer cells are exposed to otherwise poorly permeant chemotherapy agents, with consequent increased cytotoxicity. The codification of the procedure in 2006 led to a broad diffusion of the procedure, mainly in Europe, and since then, the progressive clinical experience, together with the emerging technologies, have extended the range of its application. Herein, we review the key advances in the ECT field since the European Standard Operating Procedures on ECT (ESOPE) 2006 guidelines and discuss the emerging clinical data on the new ECT indications. First, technical developments have improved ECT equipment, with custom electrode probes and dedicated tools supporting individual treatment planning in anatomically challenging tumors. Second, the feasibility and short-term efficacy of ECT has been established in deep-seated tumors, including bone metastases, liver malignancies, and pancreatic and prostate cancers (long-needle variable electrode geometry ECT), and gastrointestinal tumors (endoscopic ECT). Moreover, pioneering studies indicate lung and brain tumors as suitable future targets. A further advance relates to new combination strategies with immunotherapy, gene electro transfer (GET), calcium EP, and radiotherapy. Finally and fourth, cross-institutional collaborative groups have been established to refine procedural guidelines, promote clinical research, and explore new indications.

Electrolytic ablation enables cancer cell targeting through pH modulation

Minimally invasive ablation strategies enable locoregional treatment of tumors. One such strategy, electrolytic ablation, functions through the local delivery of direct current without thermal effects, facilitating enhanced precision. However, the clinical application of electrolytic ablation is limited by an incompletely characterized mechanism of action. Here we show that acid and base production at the electrodes precipitates local pH changes causing the rapid cell death that underlies macroscopic tumor necrosis at pH > 10.6 or < 4.8. The extent of cell death can be modulated by altering the local buffering capacity and antioxidant availability. These data demonstrate that electrolytic ablation is distinguished from other ablation strategies via its ability to induce cellular necrosis by directly altering the tumor microenvironment. These findings may enable further development of electrolytic ablation as a curative therapy for primary, early stage tumors.

Amorphous liquid metal electrodes enabled conformable electrochemical therapy of tumors

Electrochemical treatment of tumors (EChT) has recently been identified as a very effective way for local tumor therapy. However, hindered by the limited effective area of a single rigid electrode, multiple electrodes are often recruited when tackling large tumors, where too many electrodes not only complicate the clinical procedures but also aggravate patients' pain. Here we present a new conceptual electric stimulation tumor therapy through introducing the injectable liquid metal electrodes, which can adapt to complex tumor shapes so as to achieve desired therapeutic performance. This approach can offer evident merits for dealing with the complex physiological situations, especially for those irregular body cavities like stomach, colon, rectum or even blood vessel etc., which are hard to tackle otherwise. As it was disclosed from the conceptual experiments that, Unlike traditional rigid and uncomfortable electrodes, liquid metal possesses high flexibility to attach to any crooked biological position to deliver and adjust targeted electric field to fulfill anticipated tumor destruction. And such amorphous electrodes exhibit rather enhanced treatment effect of tumors. Further, we also demonstrate that EChT with liquid metal electrodes produced more electrochemical products during electrolysis. Transformations with the shapes of liquid metal provided an easily regulatable strategy to improve EChT efficiency, which can conveniently aid to achieve better output compared to multiple electrodes. In vivo EChT of tumors further clarified the effect of liquid metal electrodes in retarding tumor growth and increasing life spans.

Cryoelectrolysis; an acute case study in the pig liver

We report results from an acute, single case study in the pig liver on the effects of a tissue ablation protocol (we named cryoelectrolysis) in which 10 min of cryosurgery, with a commercial cryosurgical probe, are delivered after 10 min of electrolysis generated by a current of about 60 mA. The histological appearance of tissue treated with cryoelectrolysis is compared with the appearance of tissue treated with 10 min of cryosurgery alone and with 10 min of electrolysis alone. Histology done after 3 h survival shows that the mixed rim of live and dead cells found around the ablated lesion in both cryosurgery and electrolytic ablation is replaced by a sharp margin between life and dead cells in cryoelectrolysis. The appearance of the dead cells in each, cryoelectrolysis, cryosurgery and electrolytic ablation is different. Obviously, this is an acute study and the results are only relevant to the conditions of this study. There is no doubt that additional acute and chronic studies are needed to strengthen and expand the findings of this study.

Histopathological findings in colorectal liver metastases after electrochemotherapy

Electrochemotherapy of colorectal liver metastases has been proven to be feasible, safe and effective in a phase I/II study. In that study, a specific group of patients underwent two-stage operation, and the detailed histopathological evaluation of the resected tumors is presented here. Regressive changes in electrochemotherapy-treated liver metastases were evaluated after the second operation (in 8-10 weeks) in 7 patients and 13 metastases when the treated metastases were resected. Macroscopic and microscopic changes were analyzed. Electrochemotherapy induced coagulation necrosis in the treated area encompassing both tumor and a narrow band of normal tissue. The area became necrotic, encapsulated in a fibrous envelope while preserving the functionality of most of the vessels larger than 5 mm in diameter and a large proportion of biliary structures, but the smaller blood vessels displayed various levels of damage. At the time of observation, 8-10 weeks after electrochemotherapy, regenerative changes were already seen in the peripheral parts of the treated area. This study demonstrates regressive changes in the whole electrochemotherapy-treated area of the liver. Further evidence of disruption of vessels less than 5 mm in diameter and preservation of the larger vessels by electrochemotherapy is provided. These findings are important because electrochemotherapy has been indicated for the therapy of metastases near major blood vessels in the liver to provide a safe approach with good antitumor efficacy.

Synergistic Combination of Electrolysis and Electroporation for Tissue Ablation

Electrolysis, electrochemotherapy with reversible electroporation, nanosecond pulsed electric fields and irreversible electroporation are valuable non-thermal electricity based tissue ablation technologies. This paper reports results from the first large animal study of a new non-thermal tissue ablation technology that employs "Synergistic electrolysis and electroporation" (SEE). The goal of this pre-clinical study is to expand on earlier studies with small animals and use the pig liver to establish SEE treatment parameters of clinical utility. We examined two SEE methods. One of the methods employs multiple electrochemotherapy-type reversible electroporation magnitude pulses, designed in such a way that the charge delivered during the electroporation pulses generates the electrolytic products. The second SEE method combines the delivery of a small number of electrochemotherapy magnitude electroporation pulses with a low voltage electrolysis generating DC current in three different ways. We show that both methods can produce lesion with dimensions of clinical utility, without the need to inject drugs as in electrochemotherapy, faster than with conventional electrolysis and with lower electric fields than irreversible electroporation and nanosecond pulsed ablation.

Magnetic Resonance-Monitored Coaxial Electrochemical Ablation--Preliminary Evaluation of Technical Feasibility

PURPOSE

To evaluate the technical feasibility of a coaxial electrode configuration to rapidly create a mechanically defined electrochemical ablation zone monitored by magnetic resonance (MR) imaging in real time.

MATERIALS AND METHODS

A direct current generator supplied the nitinol cathode cage and central platinum anode for coaxial electrochemical ablation. Safety and efficacy were evaluated by measuring local pH, temperature, and current scatter in saline solutions. Ablation zone diameters of 3-6 cm (n = 72) were created on ex vivo bovine liver and verified by gross pathology. Feasibility of MR monitoring was evaluated using 8 swine livers to create ablations of 3 cm (n = 12), 4 cm (n = 4), and 5 cm (n = 4) verified by histology.

RESULTS

Local pH was 3.2 at the anode and 13.8 at the cathode. Current scatter was negligible. Ablation progress increased relative to local ion concentration, and MR signal changes corresponded to histologic findings. In the ex vivo model, the times to achieve complete ablation were 15 minutes, 20 minutes, 35 minutes, and 40 minutes for diameters of 3 cm, 4 cm, 5 cm, and 6 cm, respectively. Ablation times for the in situ model were 15 minutes, 35 minutes, and 50 minutes for 3 cm, 4 cm, and 5 cm, respectively.

CONCLUSIONS

The coaxial configuration mechanically defined the electrochemical ablation zone with times similar to comparably sized thermal ablations. MR compatibility allowed for real-time monitoring of ablation progress.

Preclinical Study of Locoregional Therapy of Hepatocellular Carcinoma by Bioelectric Ablation with Microsecond Pulsed Electric Fields (μsPEFs)

Unresectable hepatocellular carcinoma (HCC) needs locoregional ablation as a curative or downstage therapy. Microsecond Pulsed Electric Fields (μsPEFs) is an option. A xenograft tumor model was set up on 48 nude mice by injecting human hepatocellular carcinoma Hep3B cells subcutaneously. The tumor-bearing mice were randomly divided into 3 groups: μsPEFs treated, sham and control group. μsPEFs group was treated by μsPEFs twice in 5 days. Tumor volume, survival, pathology, mitochondria function and cytokines were followed up. μsPEFs was also conducted on 3 swine to determine impact on organ functions. The tumors treated by μsPEFs were completely eradicated while tumors in control and sham groups grew up to 2 cm(3) in 3 weeks. The μsPEFs-treated group indicated mitochondrial damage and tumor necrosis as shown in JC-1 test, flow cytometry, H&E staining and TEM. μsPEFs activates CD56+ and CD68+ cells and inhibits tumor proliferating cell nuclear antigen. μsPEFs inhibits HCC growth in the nude mice by causing mitochondria damage, tumor necrosis and non-specific inflammation. μsPEFs treats porcine livers without damaging vital organs. μsPEFs is a feasible minimally invasive locoregional ablation option.

Combining Electrolysis and Electroporation for Tissue Ablation

Electrolytic ablation is a method that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. This study was designed to explore the hypothesis stating that electrolytic ablation can be made more effective when the electrolysis-producing electric charges are delivered using electric pulses with field strength typical in reversible electroporation protocols. (For brevity we will refer to tissue ablation protocols that combine electroporation and electrolysis as E(2).) The mechanistic explanation of this hypothesis is related to the idea that products of electrolysis generated by E(2) protocols can gain access to the interior of the cell through the electroporation permeabilized cell membrane and therefore cause more effective cell death than from the exterior of an intact cell. The goal of this study is to provide a first-order examination of this hypothesis by comparing the charge dosage required to cause a comparable level of damage to a rat liver, in vivo, when using either conventional electrolysis or E(2) approaches. Our results show that E(2) protocols produce tissue damage that is consistent with electrolytic ablation. Furthermore, E(2) protocols cause damage comparable to that produced by conventional electrolytic protocols while delivering orders of magnitude less charge to the target tissue over much shorter periods of time.

Intraoperative electrochemotherapy of colorectal liver metastases

BACKGROUND AND OBJECTIVES

Electrochemotherapy is effective in treatment of various cutaneous tumors and could be translated into treatment of deep-seated tumors. With this aim a prospective pilot study was conducted to evaluate feasibility, safety, and efficacy of intraoperative electrochemotherapy in the treatment of colorectal liver metastases.

METHODS

Electrochemotherapy with bleomycin was performed during open surgery, by insertion of long needle electrodes into and around the tumor according to the individualized pretreatment plan.

RESULTS

A 29 metastases in 16 patients were treated in 16 electrochemotherapy sessions. No immediate (intraoperative) and/or postoperative serious adverse events related to electrochemotherapy were observed. Radiological evaluation of all the treated metastases showed 85% complete responses and 15% partial responses. In a group of seven patients that underwent a second operation at 6-12 weeks after the first one, during which electrochemotherapy was performed, the histology of resected metastases treated by electrochemotherapy showed less viable tissue (P = 0.001) compared to non-treated ones.

CONCLUSIONS

Electrochemotherapy of colorectal liver metastases proved to be feasible, safe, and efficient treatment modality, providing its specific place in difficult to treat metastases, located in the vicinity of major hepatic vessels, not amenable to surgery or radiofrequency ablation.

Nanosecond pulsed electric field inhibits cancer growth followed by alteration in expressions of NF-κB and Wnt/β-catenin signaling molecules

Cancer remains a leading cause of death worldwide and total number of cases globally is increasing. Novel treatment strategies are therefore desperately required for radical treatment of cancers and long survival of patients. A new technology using high pulsed electric field has emerged from military application into biology and medicine by applying nsPEF as a means to inhibit cancer. However, molecular mechanisms of nsPEF on tumors or cancers are still unclear. In this paper, we found that nsPEF had extensive biological effects in cancers, and clarified its possible molecular mechanisms in vitro and in vivo. It could not only induce cell apoptosis via dependent-mitochondria intrinsic apoptosis pathway that was triggered by imbalance of anti- or pro-apoptosis Bcl-2 family proteins, but also inhibit cell proliferation through repressing NF-κB signaling pathway to reduce expressions of cyclin proteins. Moreover, nsPEF could also inactivate metastasis and invasion in cancer cells by suppressing Wnt/β-Catenin signaling pathway to down-regulating expressions of VEGF and MMPs family proteins. More importantly, nsPEF could function safely and effectively as an anti-cancer therapy through inducing tumor cell apoptosis, destroying tumor microenvironment, and depressing angiogenesis in tumor tissue in vivo. These findings may provide a creative and effective therapeutic strategy for cancers.