Irreversible electroporation (IRE) of the prostate is a focal therapy technique used to treat prostate cancer. IRE is performed using the NanoKnife® system. This involves administering electrical pulses of varying strength and for periods of just a few microseconds to destroy the cell membrane of the tumour cells. It is as if an electronic scalpel is opening the cell membrane, hence the name “NanoKnife”.
IRE is suitable for prostate cancer patients who qualify for focal therapy. It is also a potential alternative for patients who do not want surgery or radiotherapy or who are not eligible for these forms of treatment for health reasons.
Treating prostate cancer using IRE involves inserting thin electrodes into the cancerous areas via the perineum. Voltages of several thousand volts are built up between each set of two electrodes. These strong electrical fields create pores in the cell membranes of the cancer cells found within the treatment area. These pores can no longer close, which is why the procedure is referred to as “irreversible electroporation”. The cancer cells are killed due to the formation of these pores.
IRE requires a brief stay in hospital. Patients are discharged the day after treatment. Before the operation can begin, the patient is put under anaesthetic and a catheter is inserted to protect the urethra and prevent urinary retention following the procedure. The catheter is generally removed after just a few days.
The procedure must be performed under general anaesthesia. Otherwise, the strong electrical pulses would cause severe muscle tension. General anaesthesia is required because the relaxation of the muscles also affects the respiratory muscles. During the procedure, a guidance grid is placed against the ultrasound probe once this has been inserted into the rectum. This grid contains a coordinate system and guidance slots to enable the electrodes to be inserted accurately.
The grid coordinate system is aligned with the coordinates from the MRI and the ultrasound, so that the needles are inserted in the right place. Depending on the size of the tumour, two to six needles are inserted through the perineum in such a way that the cancerous area is surrounded. They are placed at a distance of 1.5 to 2 centimetres from one another, and inserted into the tissue to the same depth.
As with all tumour treatments, the healing process must be carefully monitored following IRE. This allows any complications or tumour recurrence to be detected at an early stage. An MRI of the prostate is recommended after six to eight weeks to confirm that the treatment was successful. Follow-up care also includes regular testing of PSA levels and a prostate biopsy.
No serious complications were observed in prostate cancer patients treated with IRE in any of the studies conducted to date (1-7).
The majority of patients did not become incontinent following treatment. In just one study, two patients were slightly incontinent after 12 months (1).
During the follow-up period of 6 to 12 months, 66% to 100% of patients were able to maintain an erection (table).
In the studies completed to date, IRE has been found to be a safe treatment method (4, 6, 8). Due to its localised application, IRE also has less of an impact on quality of life and patients need to spend less time in hospital after treatment. Following local thermal ablation procedures (cryotherapy, HIFU), a transition zone is discernible between the ablated and non-ablated tissue. Cells damaged by the ablation process can be found in this zone.
After IRE, there is a clear-cut demarcation line between the healthy and treated area (9). This allows neighbouring structures such as blood vessels, nerves and the urethra to be protected (2, 10). In contrast to surgical procedures, patients suffer no disfiguring scars or abdominal adhesion.
Although the results recorded in the first published studies are promising, there is currently no long-term data on tumour control. In the study by van den Bos, a follow-up biopsy performed 6 to 12 months after IRE on patients who were treated with a safety margin of 10 mm found that 8.6% had a new tumour in the treated area and 9.8% had a tumour outside of the treated area. Following the collection of samples, 81.6% of all patients were therefore found to be tumour free. To put it more simply, 4 out of 5 men were tumour free 6 to 12 months after receiving IRE.
At present, alta uro in Basel is the only medical practice in Switzerland to offer IRE as a treatment for prostate cancer.
2. Onik G, Rubinsky B. Irreversible electroporation: first patient experience focal therapy of prostate cancer. Irreversible Electroporation: Springer; 2010. p. 235-47.
3. Scheltema MJ, Chang JI, Böhm M, et al. Pair-matched patient-reported quality of life and early oncological control following focal irreversible electroporation versus robot-assisted radical prostatectomy. World journal of urology. 2018:1-7.
4. Ting F, Tran M, Böhm M, et al. Focal irreversible electroporation for prostate cancer: functional outcomes and short-term oncological control. Prostate cancer and prostatic diseases. 2016;19(1):46.
5. Valerio M, Dickinson L, Ali A, et al. Nanoknife Electroporation Ablation Trial: a prospective development study investigating focal irreversible electroporation for localized prostate cancer. The Journal of urology. 2017;197(3):647-54.
6. Valerio M, Stricker PD, Ahmed HU, et al. Initial assessment of safety and clinical feasibility of irreversible electroporation in the focal treatment of prostate cancer. Prostate cancer and prostatic diseases. 2014;17(4):343.
7. van den Bos W, Scheltema MJ, Siriwardana AR, et al. Focal irreversible electroporation as primary treatment for localized prostate cancer. BJU international. 2018;121(5):716-24.
8. Wagstaff PG, Buijs M, van den Bos W, et al. Irreversible electroporation: state of the art. OncoTargets and therapy. 2016;9:2437.
9. Van den Bos W, De Bruin D, Jurhill R, et al. The correlation between the electrode configuration and histopathology of irreversible electroporation ablations in prostate cancer patients. World journal of urology. 2016;34(5):657-64.
10. Li W, Fan Q, Ji Z, Qiu X, Li Z. The effects of irreversible electroporation (IRE) on nerves. PloS one. 2011;6(4):e18831.