This study introduces a new method for minimally invasive treatment of cancer-the ablation of undesirable tissue through the use of irreversible electroporation. Electroporation is the permeabilization of the cell membrane due to an applied electric field. As a function of the field amplitude and duration, the permeabilization can be reversible or irreversible. Over the last decade, reversible electroporation has been intensively pursued as a very promising technique for the treatment of cancer. It is used in combination with cytotoxic drugs, such as bleomycin, in a technique known as electrochemotherapy. However, irreversible electroporation was completely ignored in cancer therapy. We show through mathematical analysis that irreversible electroporation can ablate substantial volumes of tissue, comparable to those achieved with other ablation techniques, without causing any detrimental thermal effects and without the need of adjuvant drugs. This study suggests that irreversible electroporation may become an important and innovative tool in the armamentarium of surgeons treating cancer.

Irreversible electroporation (IRE) is a new tissue ablation technique in which micro to millisecond electrical pulses are delivered to undesirable tissue to produce cell necrosis through irreversible cell membrane permeabilization. IRE affects only the cell membrane and no other structure in the tissue. The goal of the study is to test our IRE tissue ablation methodology in the pig liver, provide first experience results on long term histopathology of IRE ablated tissue, and discuss the clinical implications of the findings. The study consists of: a) designing an IRE ablation protocol through a mathematical analysis of the electrical field during electroporation; b) using ultrasound to position the electroporation electrodes in the predetermined locations and subsequently to monitor the process; c) applying the predetermined electrotroporation pulses; d) performing histolopathology on the treated samples for up to two weeks after the procedure; and e) correlating the mathematical analysis, ultrasound data, and histology. We observed that electroporation affects tissue in a way that can be imaged in real time with ultrasound, which should facilitate real time control of electroporation during clinical applications. We observed cell ablation to the margin of the treated lesion with several cells thickness resolution. There appears to be complete ablation to the margin of blood vessels without compromising the functionality of the blood vessels, which suggests that IRE is a promising method for treatment of tumors near blood vessels (a significant challenge with current ablation methods). Consistent with the mechanism of action of IRE on the cell membrane only, we show that the structure of bile ducts, blood vessels, and connective tissues remains intact with IRE. We report extremely rapid resolution of lesions, within two weeks, which is consistent with retention of vasculature. We also document tentative evidence for an immunological response to the ablated tissue. Last, we show that mathematical predictions with the Laplace equation can be used in treatment planning.The IRE tissue ablation technique, as characterized in this report, may become an important new tool in the surgeon armamentarium.

The ability to replace organs and tissues on demand could save or improve millions of lives each year globally and create public health benefits on par with curing cancer. Unmet needs for organ and tissue preservation place enormous logistical limitations on transplantation, regenerative medicine, drug discovery, and a variety of rapidly advancing areas spanning biomedicine. A growing coalition of researchers, clinicians, advocacy organizations, academic institutions, and other stakeholders has assembled to address the unmet need for preservation advances, outlining remaining challenges and identifying areas of underinvestment and untapped opportunities. Meanwhile, recent discoveries provide proofs of principle for breakthroughs in a family of research areas surrounding biopreservation. These developments indicate that a new paradigm, integrating multiple existing preservation approaches and new technologies that have flourished in the past 10 years, could transform preservation research. Capitalizing on these opportunities will require engagement across many research areas and stakeholder groups. A coordinated effort is needed to expedite preservation advances that can transform several areas of medicine and medical science.

This paper reports results of in vivo experiments that confirm the feasibility of a new minimally invasive method for tissue ablation, irreversible electroporation (IRE). Electroporation is the generation of a destabilizing electric potential across biological membranes that causes the formation of nanoscale defects in the lipid bilayer. In IRE, these defects are permanent and lead to cell death. This paper builds on our earlier theoretical work and demonstrates that IRE can become an effective method for nonthermal tissue ablation requiring no drugs. To test the capability of IRE pulses to ablate tissue in a controlled fashion, we subjected the livers of male Sprague-Dawley rats to a single 20-ms-long square pulse of 1000 V/cm, which calculations had predicted would cause nonthermal IRE. Three hours after the pulse, treated areas in perfusion-fixed livers exhibited microvascular occlusion, endothelial cell necrosis, and diapedeses, resulting in ischemic damage to parenchyma and massive pooling of erythrocytes in sinusoids. However, large blood vessel architecture was preserved. Hepatocytes displayed blurred cell borders, pale eosinophilic cytoplasm, variable pyknosis and vacuolar degeneration. Mathematical analysis indicates that this damage was primarily nonthermal in nature and that sharp borders between affected and unaffected regions corresponded to electric fields of 300-500 V/cm.

We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 µs at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%), in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation.