Introduction
IRE or irreversible electroporation, is a form of focal therapy that utilizes pulsatile electrical currents to remove or destroy tissues. This treatment is a promising option for patients with low or intermediate-risk prostate cancer or patients with a high cancer-risk progression. This treatment modality is still under research and studies showed that it is a safe procedure that offers low-risk poor functional outcomes with a good short-term oncological outcome.
What Is the Aim and Mechanism of Focal Irreversible Electroporation?
-
The aim and mechanism of focal irreversible electroporation are to achieve the outcomes of radical treatment while preserving the functional outcome and reducing the rate of adverse effects.
-
The mechanism of IRE is the destabilization of the cell membrane, causing an alteration in the shape of the membrane and forming nanopores.
-
The extensive permeability of the cell disrupts the osmotic balance, leading to irreversible damage and a process called apoptosis.
-
This method is now refined to administer electrical pulses at a level to cause the death of cells and keeps the procedure below a harmful thermal threshold.
-
In structures like the blood vessels, IRE decreases smooth muscle cells and maintains the connective tissue matrix.
-
Hence it is effective in lesions in the liver where the bile duct and hepatic vessel damage are lethal.
-
In prostate cancer patients, preserving the neurovascular bundles can result in the preservation of erectile dysfunction and continence, thereby increasing the quality of a person’s life.
-
The initial trials of this therapy had shown promising results on both the functional and oncological outcomes. However, more information on its clinical performance is needed before healthcare practitioners can integrate irreversible electroporation into routine clinical practice.
How Is the Irreversible Electroporation Technique Conducted?
The IRE technique consists of different phases. They include patient preparation, field visualization, device setting up, needle insertion, and treatment delivery. All the procedures are performed in an operation theatre.
-
Patient Preparation - The patient is transferred into an operating bed, and general anesthesia is administered. A urethral catheter is inserted after placing the patient in a lithotomy position.
-
Visualization of the Field - In the next phase of the treatment, after placing the patient in the position, the treatment field is visualized. A transrectal ultrasound is inserted, and the prostate gland's three-dimensional measures, like the axial, coronal, and sagittal planes, are observed. The anatomical landmarks, including the neck of the urinary bladder, urethra, angles of the prostatic seminal vesicles, edge of the prostate base, and external sphincter, are identified and marked in an axial and sagittal plane. The location relative to other structures and target lesions is also visualized through the axial plane grid.
-
Needle Insertion - An IRE 19-guage monopolar electrode needle will begin the visualization of the target lesion. It is guided by imaging, and the first needle is inserted by considering the parallel orientation and distances between the apex and the base. Through the axial view, the needle is guided to a certain three-dimensional and relative position from the structures like the prostate capsule and urethra. The other remaining needles are then inserted in the same pattern. During an IRE procedure, the electrical pulses fired can cause unnecessary muscle contractions, and the induction of deep muscle paralysis is necessary to get the precision of the procedure. The muscle relaxant is given before the IRE device is connected in preparation for the electric pulses.
-
Setting Up of the Device - After the needles are inserted, they are connected to the IRE device. The IRE device is a low-energy direct current generator controlled by computer-based treatment planning software. The distance between electrodes is manually entered into the device software, which will provide a visualization of the electrode placement and estimated ablation zone in the axial image. The device is set to deliver around 90 pulses in 10, and a brief recharge time is present between every set. The pulse duration is 70 ms, separated by 100 ms between the electrode pairs to achieve a current between 20 to 40A. The voltage is usually within 1200 - 1800 volts per centimeter with a maximum of 3000 v/cm, and it is usually chosen depending on the distance between electrodes. This voltage range is optimal to ensure complete ablation without any heat damage and prevent undertreatment simultaneously. The 10 pulses delivered initially act as a “pulse test” to check full muscle paralysis, as unnecessary muscle contractions alter the needle position and cause a change in the zone of ablation. This pulse test will verify whether the correct voltage is given between needles to ensure the treatment does not reach a thermal threshold. Necessary adjustments are made, and the remaining 80 pulses are given when optimized.
-
Delivery of the Treatment - After the needles are kept in place, the operator starts the device once the parameters are entered like needle position, active length exposure into the device, and relative needle distances. The device automatically derives a voltage between the needles to create an electric field. While throughout the treatment, the operator should hold the needles firmly to prevent ablation. The axial and sagittal views should be closely watched to make sure that the ablated area is the one that was intended. After completion of the treatment, needles are removed, and the perineum area is compressed manually for about one minute.
What Are the Functional, Oncological, and Imaging Outcomes of Focal Irreversible Electroporation?
-
Functional Outcome - Post the procedure, irreversible electroporation can preserve erectile function and urinary function at a relatively high rate. Studies showed that the potency rate range from around 77 % to 100 % at a 6 to 12 month follow-up.
-
Oncological Outcome - The post-IRE oncological outcomes are based on a combination of histology, imaging, and pathology to identify whether the prostate cancer is present or absent.
-
Imaging Outcome - Studies show that the treatment ablation is easily seen during an early post-treatment magnetic resonance imaging (MRI) for irreversible electroporation.
What Are the Post-Focal Irreversible Electroporation Complications?
Irreversible electrophoresis has adverse outcomes even though it is minimally invasive. According to the Calvien-Dindo classification, patients experience grade I to grade II adverse effects like dysuria, urinary tract infections, mild hematuria, urinary tract infections, urgency, pain, and temporary incontinence. However, patients experienced no severe adverse effects after irreversible electroporation therapy.
Conclusion
Worldwide, prostate cancer is the most commonly seen cancer in men and is the leading cause of death in men. Even though it is lethal in advanced stages, it can be treated effectively in its localized stages. Localized prostate cancer is usually treated with radiotherapy or radical prostatectomy. However, these treatments have significant side effects post-treatment, mainly erectile dysfunction and urinary incontinence. Focal therapy has now emerged as a potential form of treatment as it achieves similar outcomes as radical treatment with decreased adverse impact and a preserving functional outcome.
