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

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.

Bronchial rheoplasty for chronic bronchitis: 2-year results from a US feasibility study with RheOx

INTRODUCTION

Chronic bronchitis (CB), a phenotype of chronic obstructive pulmonary disease (COPD) characterised by persistent cough and mucus hypersecretion, is associated with poor outcomes despite guideline-based treatment. Bronchial rheoplasty (BR) with the RheOx system delivers non-thermal pulsed electric fields to the lower airway epithelium and submucosa to reduce mucus producing cells. Early phase clinical trials including 1-year follow-up have demonstrated reduction in airway goblet cell hyperplasia and improvement in CB symptoms.

METHODS

The current multicentre observational BR study enrolled 21 patients with CB at six centres in the USA, with bilateral treatment and 2-year follow-up. Entry criteria included elevated cough and sputum scores from COPD Assessment Test (CAT) and forced expiratory volume in one second<80% predicted. Safety was assessed by serious adverse event (SAE) incidence through 24 months. Clinical utility was evaluated using changes in the CAT, the St. George's Respiratory Questionnaire (SGRQ) and by comparing exacerbation rates before and following intervention.

RESULTS

No procedure-related or device-related SAEs occurred. Mean (SD) changes from baseline in CAT at 12 and 24 months were -9.0 (6.7) (p<0.0001) and -5.6 (7.1) (p<0.0047) and in SGRQ were -16.6 (13.2) (p<0.0001) and -11.8 (19.2) (p<0.0227), respectively. There was a 34% reduction in moderate and a 64% reduction in severe COPD exacerbation events compared with the year prior to treatment.

CONCLUSIONS

This study extends the findings from previous feasibility studies, demonstrating that BR can be performed safely and may significantly improve symptoms and health-related quality of life for patients with CB through 24 months.

TRAIL REGISTRATION NUMBER

NCT03631472.

Pulsed electric fields with calcium ions stimulate oxidative alternations and lipid peroxidation in human non-small cell lung cancer

Pulsed electric fields (PEFs) are commonly used to facilitate the delivery of various molecules, including pharmaceuticals, into living cells. However, the applied protocols still require optimization regarding the conditions of the permeabilization process, i.e., pulse waveform, voltage, duration, and the number of pulses in a burst. This study highlights the importance of electrochemical processes involved in the electropermeabilization process, known as electroporation. This research investigated the effects of electroporation on human non-small cell lung cancer cells (A549) in potassium (SKM) and HEPES-based buffers (SHM) using sub-microsecond and microsecond range pulses. The experiments were performed using 100 ns - 100 μs (0.6-15 kV/cm) bursts with 8 pulses in a sequence. It was shown that depending on the buffer composition, the susceptibility of cells to PEF varies, while calcium enhances the cytotoxic effects of PEF, if high cell membrane permeabilization is triggered. It was also determined that electroporation with calcium ions induces oxidative stress in cells, including lipid peroxidation (LPO), generation of reactive oxygen species (ROS), and neutral lipid droplets. Here, we demonstrated that calcium ions and optimized pulse parameters could potentiate PEF efficacy and oxidative alternations in lung cancer cells. Thus, the anticancer efficacy of PEF in lung cancers in combination with standard cytostatic drugs or calcium ions should be considered, but this issue still requires in-depth detailed studies with in vivo models.

Alternative methods for local ablation-interventional pulmonology: a narrative review

OBJECTIVE

To discuss and summarise the background and recent advances in the approach to bronchoscopic ablative therapies for lung cancer, focusing on focal parenchymal lesions.

BACKGROUND

This series focusses on the challenges highlighted by increasing recognition of the prognostically more favourable oligometastatic disease rather than the more frequent, but prognostically poor, high tumour burden metastatic disease. While surgery, stereotactic body radiation therapy (SBRT), and trans-thoracic percutaneous ablative techniques such as microwave (MWA) and radiofrequency ablation (RFA) are well recognised options for selected cases of pulmonary oligometastasis, bronchoscopic approaches to pulmonary tumour ablation are becoming realistic alternatives. An underlying tenet driving research and implementation in this domain is that percutaneous ablative techniques are obliged to traverse the pleura leading to a high rate of pneumothorax, and risks also goes up for peri-vascular lesions. Historically low yield bronchoscopic targeting of isolated peripheral tumors have significantly improved by incorporating multi-modality high resolution imaging and processing, including navigation planning and real-time image guidances (ultrasound, electromagnetic navigation, cone-beam CT). Combining advanced image guidance with ablative technology adaptations for bronchoscopic delivery opens up the options for high dose local ablative therapies that may reduce transthoracic complications and provide palliative to curative options for limited stage primary and oligometastatic diseases.

METHODS

We conduct a narrative review of the literature summarizing the history of bronchoscopic tumor ablation approaches, technical details including biologic rational for their uses, and current evidence for each modality, as well as investigations into future applications. Because of the relative paucity of prospective studies, we have been very inclusive in our inclusion of experiences from the published clinical databases.

CONCLUSIONS

Whilst surgical resection and SBRT remain the current mainstay of curative therapies for peripheral cancers, in the foreseeable future, developments and further research will see bronchoscopic ablative therapies become viable lung sparing alternatives in those deemed suitable. The future is bright.

Magnetic anchoring and guidance-assisted endoscopic irreversible electroporation for gastric mucosal ablation: a preclinical study in canine model

BACKGROUND

The aim of this study was to evaluate the feasibility, safety, and efficacy of magnetic anchoring and guidance-assisted endoscopic irreversible electroporation (MAG-IRE) for gastric mucosal ablation.

METHODS

A catheter-based, donut-like, and MAG-assisted electrode was developed. MAG-IRE for gastric mucosal ablation was performed in eight beagle canines. The parameters of one set of IRE was 500 V voltage, 100 μs pulse duration, and 99 pulses. The MAG time, operation time, success rate, and adverse events were measured. Endoscopic examination was performed from 30 min to 28 days post-IRE. Full-thickness gastric tissue was harvested by wedge biopsy for histopathological analysis.

RESULTS

30 (93.75%) of the 32 lesions were successfully ablated by MAG-IRE. The median MAG time was 300 s (IQR 120-422.5 s), and the median operation time was 491.5 s (IQR 358.3-632.5 s). No adverse events occurred. Ulceration was observed, starting from 3 days post-IRE. The mucosa healed 14 to 28 days post-IRE. Hematoxylin-Eosin (H&E) staining showed inflammatory infiltration, edema, and congestion in the ablated mucosa. Masson's Trichrome staining showed that the gastric wall and blood vessels in the ablation area were intact. TUNEL assay showed diffuse positive cells in ablated mucosa as early as 30 min post-IRE.

CONCLUSIONS

MAG-IRE for gastric mucosal ablation is feasible, safe, and effective. It can be a potential therapeutic option for minimally invasive treatment of gastric neoplasm.

Thermochromic Tissue Phantoms for Evaluating Temperature Distribution in Simulated Clinical Applications of Pulsed Electric Field Therapies

Background: Irreversible electroporation (IRE) induces cell death through nonthermal mechanisms, however, in extreme cases, the treatments can induce deleterious thermal transients. This study utilizes a thermochromic tissue phantom to enable visualization of regions exposed to temperatures above 60°C. Materials and Methods: Poly(vinyl alcohol) hydrogels supplemented with thermochromic ink were characterized and processed to match the electrical properties of liver tissue. Three thousand volt high-frequency IRE protocols were administered with delivery rates of 100 and 200 μs/s. The effect of supplemental internal applicator cooling was then characterized. Results: Baseline treatments resulted thermal areas of 0.73 cm2, which decreased to 0.05 cm2 with electrode cooling. Increased delivery rates (200 μs/s) resulted in thermal areas of 1.5 and 0.6 cm2 without and with cooling, respectively. Conclusions: Thermochromic tissue phantoms enable rapid characterization of thermal effects associated with pulsed electric field treatments. Active cooling of applicators can significantly reduce the quantity of tissue exposed to deleterious temperatures.

Acute and subacute effects of irreversible electroporation on normal common bile ducts in a rabbit model

BACKGROUND/PURPOSE

This study aimed to evaluate the acute and subacute effects of irreversible electroporation (IRE) on normal common bile ducts (CBDs).

METHODS

Cell susceptibility to IRE was assessed in vitro with cholangiocarcinoma and normal cell lines. The electric field and temperature distributions were evaluated with a two-dimensional simulation model of bile duct. In vivo bile duct IRE was performed in 28 adult rabbits.

RESULTS

Different cells showed different susceptibility to the effect of IRE, cancer cell line HUCC-T1 was the least sensitive to IRE. Simulations predicted the distributions of electric field and temperature during the IRE process, and the maximum temperature of tissue was below 43℃. Complications were observed in 8/28 animals (biliary dilatation, n = 4; biliary stricture, n = 4) by postoperative days 7, 14, and 28. Histopathological analyses revealed complete cell death with bile duct wall integrity. Bile duct epithelial recovery was completed between post-IRE days 14-28.

CONCLUSIONS

The normal CBD retains the lumen wall integrity following IRE with immediate periductal placement of the electrode. However, the risk of biliary dilatation and stricture is a reminder that the parameters of IRE need to be determined more precisely to ensure the treatment efficacy and reduce the risk of collateral damage.

Spontaneous regression of ALK fusion protein-positive non-small cell lung carcinoma: a case report and review of the literature

BACKGROUND

ALK-rearrangement is observed in < 5% non-small cell lung cancer (NSCLC) cases and prior to the advent of oral tyrosine kinase inhibitors, the natural history of oncogenic NSCLC was typically poor. Literature relating to regression of treatment-naïve NSCLC is limited, and regression without treatment has not been noted in the ALK-rearranged sub-population.

CASE PRESENTATION

A 76 year old 'never smoker' female with an ALK-rearranged left upper lobe T2 N0 NSCLC experienced a stroke following elective DC cardioversion for new atrial fibrillation. Following a good recovery, updated imaging demonstrated complete regression of the left upper lobe lesion and a reduction of the previously documented mediastinal lymph node. Remaining atelectasis was non-avid on repeat PET-CT imaging, 8 months from the baseline PET-CT. When the patient developed new symptoms 6 months later a further PET-CT demonstrated FDG-avid local recurrence. She completed 55 Gy in 20 fractions but at 18 months post-radiotherapy there was radiological progression in the lungs with new pulmonary metastases and effusion and new bone metastases. Owing to poor performance status, she was not considered fit for targeted therapy and died 5 months later.

CONCLUSION

All reported cases of spontaneous regression in lung cancer have been collated within. Documented precipitants of spontaneous regression across tumour types include biopsy and immune reconstitution; stroke has not been reported previously. The favourable response achieved with radical radiotherapy alone in this unusual case of indolent oncogenic NSCLC reinforces the applicability of radiotherapy in locally advanced ALK-rearranged tumours, in cases not behaving aggressively. As a common embolic event affecting the neurological and pulmonary vasculature is less likely, an immune-mediated mechanism may underpin the phenomenon described in this patient, implying that hitherto unharnessed principles of immuno-oncology may have relevance in oncogenic NSCLC. Alternatively, high electrical voltage applied percutaneously adjacent to the tumour during cardioversion in this patient may have induced local tumour cell lethality.

New Deployable Expandable Electrodes in the Electroporation Treatment in a Pig Model: A Feasibility and Usability Preliminary Study

The aim of the study is to evaluate the usability aspects of new deployable, expandable, electrode prototypes, in terms of suitability solutions for laparoscopic applications on the liver, endoscopic trans-oral and trans-anal procedures, electroporation segmentation in several steps, mechanical functionality (flexibility, penetrability), visibility of the electrode under instrumental guidance, compatibility of the electrode with laparoscopic/endoscopic accesses, surgical instruments, and procedural room and safety compatibility. The electroporation was performed on an animal model (Sus Scrofa Large White 60 kg) both in laparoscopy and endoscopy, under ultrasound guidance, and in open surgery. Electrodes without divergence, with needles coming out straight, parallel to each other, and electrodes with peripheral needles (four needles), diverging from the electrode shaft axis (electrode with non-zero divergence) have been tested. To cause an evaluable necrosis effect, the number of electrical pulses was increased to induce immediate liver cell death. Histological samples were analyzed by staining with Haematoxylin/Eosin or by immunohistochemical staining to confirm complete necrosis. The prototypes of expandable electrodes, tested in laparoscopy and endoscopy and in open surgery, respectively, are suitable in terms of usability, electroporation segmentation in several steps, mechanical functionality (flexibility, penetrability), visibility under instrumental guidance, compatibility with laparoscopic/endoscopic accesses, surgical instruments and procedural room safety, patient safety (no bleeding and/or perforation), and treatment efficacy (adequate ablated volume). Electroporation treatment using new deployable expandable electrode prototypes is safe and feasible. Moreover, electrode configurations allow for a gradual increase in the ablated area in consecutive steps, as confirmed by histology and immunohistochemistry.

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.

Safety and efficacy of magnetic anchoring electrode-assisted irreversible electroporation for gastric tissue ablation

BACKGROUND

Irreversible electroporation (IRE) is an emerging tissue ablation technique, which is safe for sites where thermal-basis techniques are not suitable. The aim of this study is to evaluate the safety and efficacy of magnetic anchoring electrode (MAE)-assisted IRE for normal gastric tissue ablation in a rabbit model.

METHODS

IRE (500 V, 100 μs, 99 pulses, 1 Hz) of the gastric wall was performed in 24 adult New Zealand rabbits with a novel catheter-mounted MAE with fluoroscopy and a surgical approach. Procedure time, procedure-related bleeding, perforation, and other complications were recorded. Animals were sacrificed at 30 min, 1 day, 3 days, 7 days, 14 days, and 28 days post-IRE. The stomach was removed en bloc, and the diameter of each lesion was measured. Histopathological analyses by Hematoxylin-Eosin (H&E), masson trichrome, alpha-smooth muscle action (α-SMA), and terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) were performed.

RESULTS

Gastric tissue ablation with MAE-assisted IRE was successfully performed without any interruption. No perforation or bleeding was observed during IRE or throughout the follow-up period. A demarcated hemorrhage was found in the ablated area upon gross examination. H&E staining showed complete cell death with inflammatory infiltration, edema, and hemorrhaging. TUNEL presented diffuse positive cells in the ablated area. The tissue scaffold was well preserved without damage as indicated by Masson trichrome staining. Ulceration was observed starting from 3 days post-IRE. The mucosal layer was gradually recovered and regenerated within 14-28 days. No other complication was observed post-IRE.

CONCLUSIONS

MAE-assisted IRE is safe and effective for normal gastric tissue ablation and the gastric wall recovered in 14-28 days post-IRE.