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BackTable / Urology / Article
NanoKnife Procedure Technique for Prostate Cancer: Tips and Tricks
Ishaan Sangwan • Apr 11, 2022 • 391 hits
The NanoKnife System is a new technology that is being used to perform focal ablation in intermediate grade non-metastatic prostate cancer. It uses irreversible electroporation to destroy cancer cells, and is reported to cause minimal damage to healthy tissue.
Dr. Amit Patel and Dr. Ranko Miocinovic discuss various procedural tips for performing successful NanoKnife focal ablation. We’ve provided the highlight reel in this article, and you can listen to the full podcast below.
The BackTable Urology Brief
• The NanoKnife system consists of multiple probes that should be placed equally spaced around the lesion, and remain vertically parallel to each other.
• The NanoKnife system automatically stops after a certain number of cycles. However, the wattage must be monitored to ensure that it remains within the athermal zone.
• Due to the athermal nature of the treatment, wider margins can be created with NanoKnife while minimizing harm to the underlying tissue.
• The recovery from the procedure is comparable to that from a prostate biopsy. Retention is rare, but hematospermia can occur for up to a month.
Table of Contents
(1) NanoKnife Procedure Technique
(2) The Role of Imaging in the NanoKnife Procedure
(3) Post-Operative Management of the NanoKnife Procedure
NanoKnife Procedure Technique
The NanoKnife system consists of multiple probes that must be placed geometrically around the lesion. The probes must be equally spaced, and remain vertically parallel to each other in order to function correctly. The electricity then cycles through these probes in multiple cycles, creating a zone of irreversible electroporation. The NanoKnife system cycles through a certain number of times and stops on its own once the treatment is done. However, it is important to monitor the wattage and ensure that the energy is remaining within the athermal limit.
[Dr. Amit Patel]
So you're placing your probes in a strategic sort of geometric position. You're essentially lining up your probes to surround the lesion that you're treating and the probes have to remain parallel to each other. So that's really important that they’re equally spaced and parallel from the tip of the probe to the back of the probe.
[...]
You're more or less surrounding your lesion with these electrodes, these electrode probes. And then the way the technology works, the electricity is going to cycle from one probe to the other, and then alternate to the next probe and then the third probe. And then each of the probes has current going through them.
And so there's a whole cycle. And the more probes you have, the more cycle events are going to occur between each of the probe sequences. There'll be more sequences. And as the electricity's going through from probe to probe, that's, what's creating the ablation, irreversible electroporation and causing the cell death zone.
[Dr. Jose Silva]
And how you do know when it's done? I mean, do you go by the ultrasound? Does the machine tell you to stop?
[Dr. Amit Patel]
Essentially the machine cycles through, each of the probes, at a sort of defined limit and then it stops. So you'll have a sequence of treatments and then it stops. During that time you're monitoring your wattage so you know, electroporation is athermal current, but you're monitoring your wattage because at a certain level of energy, it can become thermal so you do monitor, that energy that you're sending to make sure that you're in that athermal zone. And that's all done through the probes.
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The Role of Imaging in the NanoKnife Procedure
Imaging is a useful tool during the NanoKnife procedure because it allows for better targeting of lesions. However, it is not essential to be precise to the millimeter, since the technology treats the surrounding area along with the ablation zone. Also, due to the athermal nature of the technology, it is okay to create wider margins without risking significant morbidity to the patient. This is an advantage over techniques such as cryosurgery, where the treatment region must remain small so as to not injure the rectum and surrounding structures.
[Dr. Amit Patel]
We mostly go just by imaging. I think your percentage involvement. That's what you're asking. Percentage involvement of the core. You know, if you're targeting directly into that lesion, you're going to have a higher percentage of core involvement because you've targeted that lesion as opposed to when you were doing random biopsies.
So I think we tend to have on our targeted biopsies, we tend to have a higher percentage regardless because we've targeted that area. So we go mostly based on the imaging and the location of the positive biopsies.
[Dr. Ranko Miocinovic]
I just want to add, I know it's hard to conceptualize this, but focal ablation is not like you’re taking five millimeters and treating five by five millimeters. This really, electric field effect that's being caused. I mean, you're really, in my opinion, treating probably, quarter of a gland.
So, what I like about it is that yeah. You know where this lesion is located. But you don't have to just precisely by millimeters be right on it or around it. In essence, this is gonna ablate that entire area of the prostate. And I think that's why, even this cognitive approach that we're talking about makes sense, because you're going to ablate a certain wide area of the gland and Dr. Patel wants to say something.
[Dr. Amit Patel]
I think that's a great point because the technology has less side effects and less, no thermal damage and less side effects. It does mean that you can go wider without risking, or compromising, side effects and morbidity to the patient. So, you know, one of the things I didn't mention, which is really important, is that in cryosurgery, you can't make that ice ball as big as you want, because you're going to risk injuring the rectum and other structures, like the side wall, the muscle and the pelvic floor. With NanoKnife you can get right up to the edge of the prostate and treat that zone even slightly outside of it without significantly injuring or damaging the nerves or the neurovascular bundle. And I think to Ranko's point that's an advantage.
Post-Operative Management of the NanoKnife Procedure
After the NanoKnife procedure, patients typically have a Foley catheter inserted for three days. Dr. Miocinovic states that it’s unnecessary to do a cystoscopy after removing the catheter, as the risk of seeding a tumor is small. Most patients do not have retention once the Foley catheter is removed. Side effects include hematospermia that can continue for up to a month. Dr. Miocinovic compares the recovery and side effects of the NanoKnife procedure to that of a prostate biopsy.
[Dr. Jose Silva]
So after the treatment, you mentioned the three days Foley, do you have to do a cystoscopy afterwards for anything?
[Dr. Ranko Miocinovic]
That has not been our standard practice at all. I know, you know, I think that that the cystoscopy concept came probably from brachytherapy seeds that people would sometimes drop in the bladder, but there's no such need for this treatment.
[Dr. Jose Silva]
And have you had patients that after three days, they still have retention.
[Dr. Ranko Miocinovic]
No, I have not seen that yet. We have followed our patients obviously very closely and they may have some minor symptoms the week after the Foley comes out. And I mean, very minor. Some men have experienced hematospermia for up to a month. And I would say it's very comparable to the prostate biopsy side effects.
Podcast Contributors
Dr. Amit Patel
Dr. Amit Patel is the chairman of the urology department at Duly Health and Care in Chicago.
Dr. Ranko Miocinovic
Dr. Ranko Miocinovic is a practicing urologist with Duly Health and Care's integrated oncology program in Chicago.
Cite This Podcast
BackTable, LLC (Producer). (2022, February 9). Ep. 30 – Minimally Invasive Focal Therapy for Prostate Cancer [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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