Irreversible Electroporation Systems for Clinical Use

First Human Trial of High-Frequency Irreversible Electroporation Therapy for Prostate Cancer

Irreversible electroporation, as a nonthermal therapy of prostate cancer, has been used in clinic for several years. The mechanism of irreversible electroporation ablation is thermal independent; thus, the main structures (eg, rectum, urethra, and neurovascular bundle) in prostate are spared during the treatment, which leads to the retention of prostate function. However, various clinical trials have shown that muscle contractions occur during this therapy, which warrants deep muscle anesthesia. Use of high-frequency bipolar pulses has been proposed to reduce muscle contractions during treatment, which has already triggered a multitude of studies at the cellular and animal scale. In this study, we first investigated the efficacy and safety of high-frequency bipolar pulses in human prostate cancer ablation. There are 40 male patients with prostate cancer aged between 51 and 85 years involved in this study. All patients received 250 high-frequency bipolar pulse bursts with the repeat frequency of 1 Hz. Each burst comprised 20 individual pulses of 5 microseconds, so one burst total energized time was 100 microseconds. The number of the electrodes ranged 2 to 6, depending on tumor size. A small amount of muscle relaxant was still needed, so there were no visible muscle contractions during the pulse delivery process. Four weeks after treatment, it was found that the ablation margins were distinct in magnetic resonance imaging scans, and the prostate capsule and urethra were retained. Eight patients underwent radical prostatectomy for pathological analysis after treatment, and the results of hematoxylin and eosin staining revealed that the urethra and major vasculature in prostate have been preserved. By overlaying the electric field contour on the ablation zone, the electric field lethality threshold is determined to be 522 ± 74 V/cm. This study is the first to validate the feasibility of tumor ablation by high-frequency bipolar pulses and provide valuable experience of irreversible electroporation in clinical applications.

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.

Towards treatment planning and treatment of deep-seated solid tumors by electrochemotherapy

Background

Electrochemotherapy treats tumors by combining specific chemotherapeutic drugs with an intracellular target and electric pulses, which increases drug uptake into the tumor cells. Electrochemotherapy has been successfully used for treatment of easily accessible superficial tumor nodules. In this paper, we present the first case of deep-seated tumor electrochemotherapy based on numerical treatment planning.

Methods

The aim of our study was to treat a melanoma metastasis in the thigh of a patient. Treatment planning for electrode positioning and electrical pulse parameters was performed for two different electrode configurations: one with four and another with five long needle electrodes. During the procedure, the four electrode treatment plan was adopted and the patient was treated accordingly by electrochemotherapy with bleomycin. The response to treatment was clinically and radiographically evaluated. Due to a partial response of the treated tumor, the metastasis was surgically removed after 2 months and pathological analysis was performed.

Results

A partial response of the tumor to electrochemotherapy was obtained. Histologically, the metastasis showed partial necrosis due to electrochemotherapy, estimated to represent 40-50% of the tumor. Based on the data obtained, we re-evaluated the electrical treatment parameters in order to correlate the treatment plan with the clinical response. Electrode positions in the numerical model were updated according to the actual positions during treatment. We compared the maximum value of the measured electric current with the current predicted by the model and good agreement was obtained. Finally, tumor coverage with an electric field above the reversible threshold was recalculated and determined to be approximately 94%. Therefore, according to the calculations, a small volume of tumor cells remained viable after electrochemotherapy, and these were sufficient for tumor regrowth.

Conclusions

In this, the first reported clinical case, deep-seated melanoma metastasis in the thigh of the patient was treated by electrochemotherapy, according to a treatment plan obtained by numerical modeling and optimization. Although only a partial response was obtained, the presented work demonstrates that treatment of deep-seated tumor nodules by electrochemotherapy is feasible and sets the ground for numerical treatment planning-based electrochemotherapy.

Trial registration

EudraCT:2008-008290-54