SIU 2018: Irreversible Electroporation for Prostate Cancer

Seoul, South-Korea (UroToday.com) Dr. Sun gave an interesting talk on a new focal therapy modality for prostate cancer. He began discussing the evolution of the surgical scalpel through the years from the prehistoric flint dagger to the robotic surgical system. Despite the development of the scalpel through the years, its functions are still limited to cutting, ablating and anatomy destruction. In surgery, the surgeons must continue to try to maintain the balance between removing the lesion thoroughly, and maximally preserving the function of the organ and surrounding organs.

A good example for comparison of two different “scalpels” is the study comparing open and robotic radical prostatectomy. This study demonstrated no significant differences in the Trifecta (urinary function, erectile function and surgical margins).1 In order to reach the perfect balance of lesion removal and function preservation, using focal therapy could be one of the possible alternatives.

Focal therapy of prostate cancer is defined as a strategy to treat only part of the prostate that contains the cancer, using an energy source. The advantages of focal therapy include the fact that it is area-selective, enables preservation of anatomic structures, it is an organ-sparing approach, associated with a short hospital stay, with improved overall quality of life and it is cost-effective.

The number of focal therapy publications has grown exponentially in the last few years. It was first mentioned in the European Association of Urology (EAU) guidelines in 2005. Through the years, it progressed to the status of being potentially beneficial, to promising, and recently, to favorable. In a systematic review of focal therapy for prostate cancer, it has been shown that there are six kinds of energy that can be used for prostate cancer. The options of irreversible electroporation (IRE), laser, and photodynamic therapy have the best reported continence rate and potency rates. 2

Next, Dr. Sun discussed the focal therapy modality of IRE for prostate cancer. It is a high-voltage, low-energy current that forms the electrical field. The electrical current causes the increased permeability of cell membranes by nanoscale pores in an irreversible manner. This in turn, causes cell death through apoptosis or necrosis. 

IRE has several advantages. These include the fact that it is not thermal (no heat sink effect). Additionally, it is tissue selective and enables preservation of the extracellular matrix. It spares larger tissue structures within or near the target, such as blood vessels, nerve bundles, and urethra, thus enables to preserve function. In a systematic review of all IRE studies, one phase 1 and four phase 2 studies were included. They all demonstrated almost 100% continence rates and very high potency rates (65%-95%). Residual tumor was seen in 0-40% of cases.The known risk factors for residual tumor include lack of experience, and unstable instruments, uneven electric field, and severe muscle contraction. Because of this, the high-frequency IRE (H-FIRE) has been developed. It uses a bipolar high frequency current, thus causing a reduction of the muscle contraction and creating a more uniform electric field. The phase one study of the H-FIRE has ended, after 40 patients had been recruited. This study demonstrates favorable safety with no severe complications, complete ablation of the target areas, with good preservation of the nerve bundles. There is currently an ongoing phase 2 study, initiated in May 2018. So far, 34 patients have been recruited from 5 centers. The results so far seem very promising with good oncological results and almost no side effect profile.

In summary, IRE is a promising focal treatment modality, demonstrating a high safety profile and surprising effectiveness. The functional outcomes have been shown to be very favorable with 100% potency and erectile function rates. In the phase 2 study, PSA free survival was achieved in 82% of patients at one month following the procedure. However, the oncological effectiveness still required for long-term data.

Presented by: Yinghao Sun, Shanghai, China

References: 
  1. Yaxley JW et al. Lancet 2016
  2. Eur Urol 2018 Jul;74(1):84-91\
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre  Twitter: @GoldbergHanan at the 38th Congress of the Society of International Urology - October 4- 7, 2018 - Seoul, South Korea
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