Prostate cancer: gentle removal with irreversible electroporation

Interview with Professor Michael K. Stehling from the Prostate Center in Offenbach am Main, Germany

In many cases, a prostate cancer diagnosis leads to the removal of the entire organ. Several therapies involve a severe outcome such as impotence or incontinence. Yet a surgical intervention doesn’t always eliminate the cancer completely. That’s why physicians debate whether radical measures are actually necessary. After all, prostate cancer grows very slowly.


Photo: Michael K. Stehling

Prof. Dr. Michael K. Stehling; © Prostata Center Offenbach am Main

Compared to prostatectomy or radiation therapy, the NanoKnife® therapy practiced at the Prostate Center in Offenbach am Main removes the tumors in a gentle manner. In this interview with, Professor Michael K. Stehling explains the advantages of this focal therapy.

Professor Stehling, what was the motivation behind the creation of a center that is exclusively devoted to treating and diagnosing prostate diseases?

Michael K. Stehling: I founded the Prostate Center in 2010 and was motivated by my colleague and friend Professor Ducksoo Kim at the Boston University. The idea was based on our joint work at Harvard Medical School in the nineties. Quite early on, it was clear to us that the existing diagnostic procedures and treatment methods for prostate cancer that are connected with massive side effects were imprecise and uncomfortable and are still today.

What technology is used in the NanoKnife® therapy?

Stehling: The technology behind the NanoKnife® therapy is called irreversible electroporation (IRE). IRE uses very strong electric fields to induce pores in cell membranes. The stronger the electric fields and the higher the pulses that affect the cells, the larger they become. Eventually they no longer close. Water enters the cells until they burst. What’s crucial about this procedure is that it is a non-thermal ablation method. This way only the affected cells are being destroyed. The advantage is that the tissue infrastructure, that being everything else that tissue is composed of such as fibers, the interstitial matrix or basement membranes remain intact. With other thermal ablation methods such as radiofrequency ablation or cryoablation for example, the tissue is melted away. All tissue components are destroyed and the melted tissue lump is then removed via an external removal process. First, this causes the typical pain from the wound healing process and second, significant scarring. Radiation therapy exhibits similar problems. With IRE on the other hand, there is no pain or scarring, because the inflammatory response is not being triggered. This is also called "induced apoptosis".
Photo: Application of the NanoKnife therapy

Application of the NanoKnife® therapy during an operation; © Prostata Center Offenbach am Main

How is prostate cancer removed?

Stehling: Unlike with prostatectomy, IRE does not require surgical opening of the abdomen or pelvic area. Instead, you insert electrodes through tiny holes in the skin via the pelvic floor into the prostrate. The electrodes are exactly positioned to where they generate a treatment area that precisely includes the areas of the prostate that contain tumors. To do this, you need to know exactly where the tumors are located of course. Clinical diagnostics play a decisive role in this. The entire IRE intervention as well as monitoring and checkup subsequently take no more than 24 hours.

Which diagnostic procedures were used at the Prostate Center?

Stehling: Diagnostics with focal therapies are more elaborate than with radical therapy options. One essential component of diagnostics at the Prostate Center is magnetic resonance imaging or endorectal MRI. Accuracy is at approximately 85 percent in this case. However, the MRI is only able to illustrate macroscopic tumors, that is to say tumors that are between two to three millimeters in size. If you want to detect microscopic tumors, you can use the so-called transperineal 3D mapping biopsy. This is a systematic biopsy done through the skin of the pelvic floor, where a sample is taken exactly every five millimeters apart. Depending on how many samples are taken, we can put them together again using a special computer program and thus obtain a histological model. With the help of the MRI and the 3D biopsy, we map the relevant tumors or possibly all tumors that are currently in the prostate. These are subsequently removed using the focal IRE method.
Photo: Therapy simulation in 2D and 3D

Therapy simulation in 2D and 3D. The electrodes embrace the area that includes the tumors in the prostate; © Prostata Center Offenbach am Main

What are the advantages compared with traditional therapeutic measures such as surgery or radiation?

Stehling: There are significantly fewer side effects. In a group of 160 patients, we have treated so far, not one of them exhibits incontinence. What’s more, the percentage of impotence is also less than with other therapies. Oftentimes, impotence is only temporarily. The treatment is also completed within 24 hours. Patients exhibit no wound pain. After IRE, all other therapeutic measures remain an option. That means, if IRE were to fail, you could still perform surgery or radiation on the patient or treat him with HIFU (high-intensity focus ultrasound). That being said, IRE can also be done in succession as often as you like. This is a major advantage, because after all of the other therapy options, in particular radiation therapy, this is no longer possible or just in a very limited way.

Can you envision NanoKnife® therapy being used in a broad clinical field and replacing treatment options such as surgery and radiation at least in the prostate cancer area?

Stehling: I sincerely hope that NanoKnife® therapy or a similar gentle procedure replaces radical therapy for prostate cancer. The previously performed procedures are extremely bad and often include significant adverse effects. There are considerable recurrence rates begging the question of whether they actually provide the patient with a survival advantage. This is doubtful in many cancer stages and is proven by statistics. I believe NanoKnife® therapy to be an intermediate stage on our way to tumor-cell specific therapy. I am sure that within the next ten years there will be methods that are able to selectively target tumor cells and spare healthy somatic cells. IRE is already selective on a cellular level, but is actually not tumor-cell specific. The ultimate goal has therefore not been completely achieved yet. Yet I believe this is a very important factor, because there is a paradigm shift in cancer treatment at the moment that comes from the U.S. They assume that cancer is a chronic illness. There is still a lot of work ahead of us in this regard.
Photo: Melanie Günther; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Melanie Günther and translated from German by Elena O'Meara.