Irreversible electroporation (IRE) is an emerging form of focal therapy that utilizes pulses of electricity to ablate prostate cancer cells. At a microscopic level, the pulses of electricity create nanopores in the cell membranes, which then initiate apoptosis and permanent cell death.¹ IRE does not rely on thermal change for ablation, therefore avoiding the heat-sink effect.² Studies have demonstrated that structures such as large blood vessels and nerves are spared within the ablation zone.^3,4 Therefore, IRE has the potential to provide good oncologic control while minimizing adverse effects such as urinary incontinence and erectile dysfunction for prostate cancer patients.⁵ Early results are promising; however, more data are needed to fully understand its efficacy and optimize its use.

The procedure is performed under a general anesthetic with the patient in the lithotomy position. Nineteen-gauge needles are placed transperineally into the prostate through a biopsy grid to surround the cancer with an adequate margin. Machine software calculates the voltages required to achieve optimal ablation parameters; this is refined by the urologist. Pulses of electricity are then administered between these probes, during which caution is taken not to exceed the thermal threshold. The probes are then removed, and an indwelling catheter inserted. Patients go home on the day of the procedure, and the catheter is removed 3-5 days postoperatively.

Focal IRE is used at the moment in 2 settings: for newly diagnosed and radio-recurrent prostate cancer.⁶ To the best of our knowledge, there are 8 existing cohort studies to date exploring IRE in newly diagnosed prostate cancer, and the results are summarized in the Table. The 2 largest studies, by Blazevski et al⁷ (n=123) and Yaxley et al⁸ (n=70) found a 9.8% and 10% in-field recurrence, respectively, and 12.7% and 27.5% out-of-field recurrence rate, respectively, at 12 months of follow-up. The FIRE trial is the only published data on IRE in the radio-recurrent setting to our knowledge.⁹ Their results found a 6% in-field recurrence and 18% out-of-field recurrence rate at 12 months. Six men were found to have metastatic disease.

Table. Summary of Existing Studies Evaluating Oncologic Outcomes, Functional Outcomes, and Complications of Irreversible Electroporation on Prostate Cancer

Overall, the functional outcomes post-focal IRE are good compared to radical treatment. Potency rates in the newly diagnosed cohorts range from 85%-95%, and continence rates range from 88%-100%. Not surprisingly, in the radio-recurrent setting, the FIRE trial reported a 15% rate of potency and 93% continence. Clinically significant complications (ie, Clavien-Dindo classification 3 or greater) only occurred in radio-recurrent patients. There has been 1 case report of a rectoprostatic fistula.¹⁰

In summary, the literature shows that IRE is a safe procedure which can achieve good short-term oncologic control and low side-effect rates. Patient selection remains the key to improving outcomes, in particular decreasing rates of out-of-field recurrence overall and metastases rates in the radio-recurrent patients. New imaging modalities such as prostate-specific membrane antigen positron emission tomography-CT may help in this regard. Future studies need to incorporate larger cohort sizes and longer follow-up. Most importantly, consensus for study outcomes and follow-up across all focal therapy modalities needs to be reached in order to progress these new technologies closer toward routine clinical management.