Evaluation of Resistance as a Measure of Successful Tumor Ablation During Irreversible Electroporation of the Pancreas

Multi-disciplinary management of locally advanced pancreatic cancer with irreversible electroporation

The essential diagnosis for LAPC is based on high-quality cross-sectional imaging, which demonstrates tumor invasion into the celiac/superior mesenteric arteries and/or superior mesenteric/portal venous system that is not reconstructable. The optimal management of these patients is evolving quickly with the advent of newer chemotherapeutics, radiation, and non-thermal ablation modalities. This review will present the current status of initial chemotherapy, surgical therapy, ablative therapy, and radiation therapy for patients with nonmetastatic locally advanced unresectable pancreatic cancer.

Bipolar Microsecond Pulses and Insulated Needle Electrodes for Reducing Muscle Contractions During Irreversible Electroporation

OBJECTIVE

To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo.

METHODS

An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer.

RESULTS

With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined.

CONCLUSION

This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction.

SIGNIFICANCE

The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE.

Irreversible electroporation for the ablation of pancreatic malignancies: A patient-specific methodology

BACKGROUND AND OBJECTIVES

Irreversible Electroporation (IRE) is a focal ablation technique highly attractive to surgical oncologists due to its non-thermal nature that allows for eradication of unresectable tumors in a minimally invasive procedure. In this study, our group sought to address the challenge of predicting the ablation volume with IRE for pancreatic procedures.

METHODS

In compliance with HIPAA and hospital IRB approval, we established a pre-treatment planning methodology for IRE procedures in pancreas, which optimized treatment protocols for individual cases of locally advanced pancreatic cancer (LAPC). A new method for confirming treatment plans through intraoperative monitoring of tissue resistance was also proved feasible in three patients.

RESULTS

Results from computational models showed good correlation with experimental data available in the literature. By implementing the proposed resistance measurement system 210 ± 26.1 (mean ± standard deviation) fewer pulses were delivered per electrode-pair.

CONCLUSION

The proposed physics-based pre-treatment plan through finite element analysis and system for actively monitoring resistance changes can be paired to significantly reduce ablation times and risk of thermal effects during IRE procedures for LAPC.

Irreversible electroporation for the treatment of pancreatic neuroendocrine tumors

Backgrounds/Aims

Resection or enucleation is currently the treatment of choice for small pancreatic neuroendocrine tumors (NETs). Irreversible electroporation is a novel ablative method that is used for locally advanced pancreatic adenocarcinoma, but little data exists for its use for pancreatic NETs. We report an early experience of IRE for early pancreatic NETs.

Methods

Between April 2014 and March 2015, 3 patients with small (<2 cm) pancreatic NETs were treated with percutaneous IRE.

Results

There were no adverse effects during the procedure. Mean hospital stay was 2.6 days. All patients remained disease free on 12-19 months follow up. One patient developed recurrent pancreatitis with pseudocyst formation.

Conclusions

IRE for small tumors of the pancreas is practical and may offer advantages over other thermal ablative techniques, since it preserves vital structures such as blood vessels, bile and pancreatic ducts. Further data regarding the long term disease free interval is required to establish efficacy.

Irreversible electroporation in locally advanced pancreatic cancer: A call for standardization of energy delivery

Irreversible Electroporation (IRE) is used to treat locally advanced cancers, commonly of the pancreas, liver, kidney, and other soft tissues. Precise eligibility for IRE should be established in each individual patient by a multidisciplinary team based on comprehensive clinical, imaging, and laboratory assessment. Standardization of IRE technique and protocols is expected to improve safety, lead to reproducible outcomes, and facilitate further research into IRE. The present article provides a set of technical recommendations for the use of IRE in the treatment of locally advanced pancreatic cancer. J. Surg. Oncol. 2016;114:865-871. © 2016 2016 Wiley Periodicals, Inc.

The correlation between the electrode configuration and histopathology of irreversible electroporation ablations in prostate cancer patients

PURPOSE

Irreversible electroporation (IRE) is a novel minimally invasive therapy for prostate cancer using short electric pulses to ablate prostate tissue. The purpose of this study is to determine the IRE effects in prostate tissue and correlate electrode configuration with the histology of radical prostatectomy (RP) specimens. We hypothesize that the area within the electrode configuration is completely ablated and that the area within the electrode configuration is predictive for the ablated area after treatment.

METHODS

A prospective phase I/II study was conducted in 16 consecutive patients with histopathologically confirmed prostate cancer scheduled for RP. Focal or extended IRE treatment of the prostate was performed 4 weeks prior to RP. The locations of the electrodes were used to calculate the planned ablation zone. Following RP, the specimens were processed into whole-mount sections, histopathology (PA) was assessed and ablation zones were delineated. The area of the tissue alteration was determined by measuring the surface. The planned and the histological ablation zones were compared, analysed per individual patient and per protocol (focal vs. extended).

RESULTS

All cells within the electrode configuration were completely ablated and consisted only of necrotic and fibrotic tissue without leaving any viable cells. The histological ablation zone was always larger than the electrodes configuration (2.9 times larger for the 3 electrodes configuration and 2.5 times larger for the ≥4 electrode configuration). These ablation effects extended beyond the prostatic capsule in the neurovascular bundle in 13 out of 15 cases.

CONCLUSIONS

IRE in prostate cancer results in completely ablated, sharply demarcated lesions with a histological ablation zone beyond the electrode configuration. No skip lesions were observed within the electrode configuration.

CLINICAL TRIALS

ClinicalTrials.gov Identifier: NCT01790451 https://clinicaltrials.gov/ct2/show/NCT01790451.

Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation): A Review

Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC) accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA) and Irreversible Electroporation (IRE) are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on the use of these techniques have already demonstrated encouraging results in terms of safety and feasibility. Unfortunately, few studies on their efficacy are currently available. Even though some reports on the overall survival are encouraging, randomized studies are still required to corroborate these findings. This study provides an up-to-date overview and a thematic summary of the current available evidence on the application of RFA and IRE on PDAC, together with a comparison of the two procedures.

The Feasibility of a Smart Surgical Probe for Verification of IRE Treatments Using Electrical Impedance Spectroscopy

SIGNIFICANCE

Irreversible electroporation (IRE) is gaining popularity as a focal ablation modality for the treatment of unresectable tumors. One clinical limitation of IRE is the absence of methods for real-time treatment evaluation, namely actively monitoring the dimensions of the induced lesion. This information is critical to ensure a complete treatment and minimize collateral damage to the surrounding healthy tissue.

GOAL

In this study, we are taking advantage of the biophysical properties of living tissues to address this critical demand.

METHODS

Using advanced microfabrication techniques, we have developed an electrical impedance microsensor to collect impedance data along the length of a bipolar IRE probe for treatment verification. For probe characterization and interpretation of the readings, we used potato tuber, which is a suitable platform for IRE experiments without having the complexities of in vivo or ex vivo models. We used the impedance spectra, along with an electrical model of the tissue, to obtain critical parameters such as the conductivity of the tissue before, during, and after completion of treatment. To validate our results, we used a finite element model to simulate the electric field distribution during treatments in each potato.

RESULTS

It is shown that electrical impedance spectroscopy could be used as a technique for treatment verification, and when combined with appropriate FEM modeling can determine the lesion dimensions.

CONCLUSIONS

This technique has the potential to be readily translated for use with other ablation modalities already being used in clinical settings for the treatment of malignancies.

Treatment of 200 locally advanced (stage III) pancreatic adenocarcinoma patients with irreversible electroporation: safety and efficacy

OBJECTIVES

Ablative therapies have been increasingly utilized in the treatment of locally advanced pancreatic cancer (LAPC). Irreversible electroporation (IRE) is an energy delivery system, effective in ablating tumors by inducing irreversible membrane destruction of cells. We aimed to demonstrate efficacy of treatment with IRE as part of multimodal treatment of LAPC.

METHODS

From July 2010 to October 2014, patients with radiographic stage III LAPC were treated with IRE and monitored under a multicenter, prospective institutional review board-approved registry. Perioperative 90-day outcomes, local failure, and overall survival were recorded.

RESULTS

A total of 200 patients with LAPC underwent IRE alone (n = 150) or pancreatic resection plus IRE for margin enhancement (n = 50). All patients underwent induction chemotherapy, and 52% received chemoradiation therapy as well for a median of 6 months (range, 5-13 months) before IRE. IRE was successfully performed in all patients. Thirty-seven percent of patients sustained complications, with a median grade of 2 (range, 1-5). Median length of stay was 6 days (range, 4-36 days). With a median follow-up of 29 months, 6 patients (3%) have experienced local recurrence. Median overall survival was 24.9 months (range: 4.9-85 months).

CONCLUSIONS

For patients with LAPC (stage III), the addition of IRE to conventional chemotherapy and radiation therapy results in substantially prolonged survival compared with historical controls. These results suggest that ablative control of the primary tumor may prolong survival.

Bursts of Bipolar Microsecond Pulses Inhibit Tumor Growth

Irreversible electroporation (IRE) is an emerging focal therapy which is demonstrating utility in the treatment of unresectable tumors where thermal ablation techniques are contraindicated. IRE uses ultra-short duration, high-intensity monopolar pulsed electric fields to permanently disrupt cell membranes within a well-defined volume. Though preliminary clinical results for IRE are promising, implementing IRE can be challenging due to the heterogeneous nature of tumor tissue and the unintended induction of muscle contractions. High-frequency IRE (H-FIRE), a new treatment modality which replaces the monopolar IRE pulses with a burst of bipolar pulses, has the potential to resolve these clinical challenges. We explored the pulse-duration space between 250 ns and 100 μs and determined the lethal electric field intensity for specific H-FIRE protocols using a 3D tumor mimic. Murine tumors were exposed to 120 bursts, each energized for 100 μs, containing individual pulses 1, 2, or 5 μs in duration. Tumor growth was significantly inhibited and all protocols were able to achieve complete regressions. The H-FIRE protocol substantially reduces muscle contractions and the therapy can be delivered without the need for a neuromuscular blockade. This work shows the potential for H-FIRE to be used as a focal therapy and merits its investigation in larger pre-clinical models.

Irreversible electroporation of locally advanced pancreatic neck/body adenocarcinoma

OBJECTIVE

Irreversible electroporation (IRE) of locally advanced pancreatic adenocarcinoma of the neck has been used to palliate appropriate stage 3 pancreatic cancers without evidence of metastasis and who have undergone appropriate induction therapy. Currently there has not been a standardized reported technique for pancreatic mid-body tumors for patient selection and intra-operative technique.

PATIENTS

Subjects are patients with locally advanced pancreatic adenocarcinoma of the body/neck who have undergone appropriate induction chemotherapy for a reasonable duration.

MAIN OUTCOME MEASURES

Technique of open IRE of locally advanced pancreatic adenocarcinoma of the neck/body is described, with the emphasis on intra-operative ultrasound and intra-operative electroporation management.

RESULTS

The technique of open IRE of the pancreatic neck/body with bracketing of the celiac axis and superior mesenteric artery with continuous intraoperative ultrasound imaging and consideration of intraoperative navigational system is described.

CONCLUSIONS

IRE of locally advanced pancreatic adenocarcinoma of the body/neck is feasible for appropriate patients with locally advanced unresectable pancreatic cancer.

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.

Efficacy of irreversible electroporation in human pancreatic adenocarcinoma: advanced murine model

Irreversible electroporation (IRE) is a promising cell membrane ablative modality for pancreatic cancer. There have been recent concerns regarding local recurrence and the potential use of IRE as a debulking (partial ablation) modality. We hypothesize that incomplete ablation leads to early recurrence and a more aggressive biology. We created the first ever heterotopic murine model by inoculating BALB/c nude mice in the hindlimb with a subcutaneous injection of Panc-1 cells, an immortalized human pancreatic adenocarcinoma cell line. Tumors were allowed to grow from 0.75 to 1.5 cm and then treated with the goal of complete ablation or partial ablation using standard IRE settings. Animals were recovered and survived for 2 days (n = 6), 7 (n = 6), 14 (n = 6), 21 (n = 6), 30 (n = 8), and 60 (n = 8) days. All 40 animals/tumors underwent successful IRE under general anesthesia with muscle paralysis. The mean tumor volume of the animals undergoing ablation was 1,447.6 mm³ ± 884). Histologically, in the 14-, 21-, 30-, and 60-day survival groups the entire tumor was nonviable, with a persistent tumor nodule completely replaced fibrosis. In the group treated with partial ablation, incomplete electroporation/recurrences (N = 10 animals) were seen, of which 66% had confluent tumors and this was a significant predictor of recurrence (P < 0.001). Recurrent tumors were also significantly larger (mean 4,578 mm³ ± SD 877 versus completed electroporated tumors 925.8 ± 277, P < 0.001). Recurrent tumors had a steeper growth curve (slope = 0.73) compared with primary tumors (0.60, P = 0.02). Recurrent tumors also had a significantly higher percentage of EpCAM expression, suggestive of stem cell activation. Tumors that recur after incomplete electroporation demonstrate a biologically aggressive tumor that could be more resistant to standard of care chemotherapy. Clinical correlation of this data is limited, but should be considered when IRE of pancreatic cancer is being considered.

Current status of Interventional Radiology in the management of Gastro-Entero-Pancreatic Neuroendocrine Tumours (GEP-NETs)

Within the group of Gastro-Entero-Pancreatic Neuroendocrine tumours (GEP-NETs), several heterogeneous malignancies are included with a variety of clinical manifestations and imaging characteristics. Often these cases are inoperable and minimal invasive treatment offered by image-guided procedures appears to be the only option. Interventional radiology offers a valid solution in the management of primary and metastatic GEP-NETs. The purpose of this review article is to describe the current status of the role of Interventional Radiology in the management of GEP-NETs.