Irreversible Electroporation: a Novel Option for Treatment of Hepatic Metastases

Ionomycin-Induced Changes in Membrane Potential Alter Electroporation Outcomes in HL-60 Cells

Previous studies have shown greater fluorophore uptake during electroporation on the anode-facing side of the cell than on the cathode-facing side. Based on these observations, we hypothesized that hyperpolarizing a cell before electroporation would decrease the requisite pulsed electric field intensity for electroporation outcomes, thereby yielding a higher probability of reversible electroporation at lower electric field strengths and a higher probability of irreversible electroporation (IRE) at higher electric field strengths. In this study, we tested this hypothesis by hyperpolarizing HL-60 cells using ionomycin before electroporation. These cells were then electroporated in a solution containing propidium iodide, a membrane integrity indicator. After 20 min, we added trypan blue to identify IRE cells. Our results showed that hyperpolarizing cells before electroporation alters the pulsed electric field intensity thresholds for reversible electroporation and IRE, allowing for greater control and selectivity of electroporation outcomes.

Safety and efficacy of irreversible electroporation in the treatment of obstructive jaundice in advanced hilar cholangiocarcinoma

BACKGROUND

Irreversible electroporation (IRE) has successfully been used for palliation of pancreatic and liver cancers due to its ability to ablate tumors without destroying nearby vital structures. To date, it has not been evaluated in patients with advanced hilar cholangiocarcinoma (AHC). This study presents a single-institution experience with IRE for management of obstructive jaundice in AHC.

METHODS

A single-institution database was queried for patients undergoing IRE for AHC after PTBD placement for relief of obstructive jaundice from 2010 to 2017 and compared to a control group treated with standard of care only (No IRE).

RESULTS

Twenty-six patients underwent IRE for AHC after PTBD replacement. Three patients experienced complications, with two experiencing severe (≥ grade 3) complications. After IRE, median time to PTBD removal was 122 days (range 0-305 days) and median catheter-free time before requiring PTBD replacement was 305 days (range 92-458 days). In comparison, the 137 control patients had an admission rate of 59% (N = 80 patients) for PTBD infection, occlusion, or catheter related problem.

CONCLUSION

IRE safely achieves biliary decompression via tumor electroporation and allows PTBD removal for an extended period of time. In appropriately selected patients with obstructive jaundice in the setting of AHC, IRE can be used to increase catheter-free days and optimize overall quality of life.

Intra - operative Anesthesia Management in Patients Undergoing Surgical Irreversible Electroporation of the Pancreas, Liver, Kidney, and Retroperitoneal Tumors

Background:

Irreversible electroporation (IRE) is a relatively new approach to the management of multiple types of locally advanced soft tissue tumors. Unique peri-procedural anesthetic management is needed in the safe and effective delivery of this therapy.

Objectives:

This study analyzed IRE therapy in relation to anesthetic management for our initial cohort and then established and validated a set of best practical guidelines for general anesthesia in patients undergoing IRE for abdominal tumors.

Patients and Methods:

An IRB-approved prospective data collection outcome protocol was utilized. This study was broken up into two cohorts as follows: the initial 38 patients (pts) undergoing IRE in which anesthetic management was not defined or optimized and then a 40-pt validation cohort to establish the most efficacious anesthetic protocols.

Results:

During IRE delivery, a deeper neuromuscular blockade is required to ensure that all retroperitoneal muscle excitation was minimized. In the initial 38-pt cohort, attempts to treat hypertension (median SBP 190, range 185–215 and median diastolic 98, range 91–115) were made with various types of anti-hypertensives with minimal-to-insufficient effects. The established inhalation was sevoflurane with an approximate median dose of 8.0 volume percentage. Analgesic management of continuous remifentanil was utilized with epidural management, which optimized HTN and tolerance to IRE therapy.

Conclusions:

Anesthetic management for IRE of soft tissue deviates from standard anesthetic medical therapy in regards to depth of neuromuscular blockade and analgesic management during IRE energy delivery. However, minor modifications in anesthesia management allow for a safe and efficient patient procedure.

Irreversible electroporation of unresectable soft tissue tumors with vascular invasion: effective palliation

Background

Irreversible electroporation (IRE) has recently been added as an additional therapeutic ablative option in patients with locally advanced cancers (LAC) involving vital structures. IRE delivers localized electric current by peri-tumoral discrete probes to attain irreversible changes in cell membrane leading to cell death. The aim of this study was to evaluate the long-term effects of IRE in the treatment of locally advanced tumors.

Methods

A prospective IRB approved evaluation of 107 consecutive patients from 7 institutions with tumors that had vascular invasion treated with IRE from 5/2010 to 1/2012. LAC was defined as primary tumor with <5 mm from major vascular structure based on pre-operative dynamic imaging or intra-operative criteria.

Results

IRE as utilized in LAC in the liver (N = 42, 40%) and pancreas (N = 37, 35%), with a median number of lesions being 2 with a mean target size of 3 cm. IRE attributable morbidity rate was 13.3% (total 29.3%) with high-grade complications seen in 4.19% (total 12.6%). No significant vascular complications were seen, and of the high-grade complications, bleeding (2), biliary complications (3) and DVT/PE (3) were the most common. Complications were more likely with pancreatic lesions (p = 0.0001) and open surgery (p = 0.001). Calculated local recurrence free survival (LRFS) was 12.7 months with a median follow up of 26 months censured at last follow up. The tumor target size was inversely associated with recurrence free survival (b = 0.81, 95% CI: 1.6 to 4.7, p value = 0.02) but this did not have a significant overall survival impact.

Conclusions

IRE represents a novel therapeutic option in patients with LAC involving vital structures that are not amenable to surgical resection. Acceptable to high local disease control and the long LRFS can be achieved with this therapy in combination with other multi-disciplinary therapies.

Evaluation of thermal injury to liver, pancreas and kidney during irreversible electroporation in an in vivo experimental model

BACKGROUND

Irreversible electroporation (IRE) is a new technique for tumour cell ablation that is reported to involve non-thermal-based energy using high voltage at short microsecond pulse lengths. In vivo assessment of the thermal energy generated during IRE has not been performed. Thermal injury can be predicted using a critical temperature model. The aim of this study was to assess the potential for thermal injury during IRE in an in vivo porcine model.

METHODS

In vivo continuous temperature assessments of 86 different IRE procedures were performed on porcine liver, pancreas, kidney and retroperitoneal tissue. Tissue temperature was measured continuously throughout IRE by means of two thermocouples placed at set distances (0·5 cm or less, and 1 cm) from the IRE probes within the treatment field. Thermal injury was defined as a tissue temperature of 54°C lasting at least 10 s. Tissue type, pulse length, probe exposure length, number of probes and retreatment were evaluated for associations with thermal injury. In addition, IRE ablation was performed with metal clips or metal stents within the ablation field to determine their effect on thermal injury.

RESULTS

An increase in tissue temperature above the animals' baseline temperature (median 36·0°C) was generated during IRE in all tissues studied, with the greatest increase found at the thermocouple placed within 0·5 cm in all instances. On univariable and multivariable analysis, ablation in kidney tissue (maximum temperature 62·8°C), ablation with a pulse length setting of 100 µs (maximum 54·7°C), probe exposure of at least 3·0 cm (maximum 52·0°C) and ablation with metal within the ablation field (maximum 65·3°C) were all associated with a significant risk of thermal injury.

CONCLUSION

IRE can generate thermal energy, and even thermal injury, based on tissue type, probe exposure lengths, pulse lengths and proximity to metal. Awareness of probe placement regarding proximity to critical structures as well as probe exposure length and pulse length are necessary to ensure safety and prevent thermal injury. A probe exposure of 2·5 cm or less for liver IRE, and 1·5 cm or less for pancreas, with maximum pulse length of 90 µs will result in safe and non-thermal energy delivery with spacing of 1·5-2·3 cm between probe pairs.

Irreversible electroporation for nonthermal tumor ablation in the clinical setting: a systematic review of safety and efficacy

PURPOSE

To provide an overview of current clinical results of irreversible electroporation (IRE), a novel, nonthermal tumor ablation technique that uses electric pulses to induce cell death, while preserving structural integrity of bile ducts and vessels.

METHODS

All in-human literature on IRE reporting safety or efficacy or both was included. All adverse events were recorded. Tumor response on follow-up imaging from 3 months onward was evaluated.

RESULTS

In 16 studies, 221 patients had 325 tumors treated in liver (n = 129), pancreas (n = 69), kidney (n = 14), lung (n = 6), lesser pelvis (n = 1), and lymph node (n = 2). No major adverse events during IRE were reported. IRE caused only minor complications in the liver; however, three major complications were reported in the pancreas (bile leak [n = 2], portal vein thrombosis [n = 1]). Complete response at 3 months was 67%-100% for hepatic tumors (93%-100% for tumors o 3 cm). Pancreatic IRE combined with surgery led to prolonged survival compared with control patients (20 mo vs 13 mo) and significant pain reduction.

CONCLUSIONS

In cases where other techniques are unsuitable, IRE is a promising modality for the ablation of tumors near bile ducts and blood vessels. This articles gives an extensive overview of the available evidence, which is limited in terms of quality and quantity. With the limitations of the evidence in mind, IRE of central liver tumors seems relatively safe without major complications, whereas complications after pancreatic IRE appear more severe. The available limited results for tumor control are generally good. Overall, the future of IRE for difficult-to-reach tumors appears promising.