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BackTable / VI / Article
Prostatic Artery Embolization: Standardization of Advanced Techniques
Bryant Schmitz • Updated Jun 20, 2023 • 514 hits
Because the procedure is still quite novel, interventional radiologists implement a variety of prostatic artery embolization (PAE) procedure techniques based on individual training, experiences, and observed outcomes. However, variations in catheter choice, endpoints, particle sizes, and use of coils or liquids can lead to inconsistent procedure outcomes. In an effort to standardize prostatic artery embolization in practice, interventional radiologist Dr. Sam Mouli explains his technique and his recommendations on particle size, coiling, liquids, and retreatment.
The BackTable Brief
• Differences in catheter and wire choice, endpoints, particle sizes, and use of coils or liquids can lead to inconsistent outcomes. Standardizing the procedure based on long-term data could improve outcomes and safety.
• Data suggests that 300 to 500-micron particles provide a good balance of efficacy and safety in de novo PAE cases. Smaller particles, while causing better infarction, may lead to off-target effects and increased risk of sexual dysfunction.
• Coiling, which involves embolizing the prostate to stasis and then coiling the parent vessel, is not typically recommended by Dr. Mouli. Its benefits for infarction and permanent embolization are unproven and it may hinder future retreatment options. In exceptional cases, coiling might be employed in patients with hematuria to prevent future bleeding, especially if they need to resume anticoagulation therapy.
• The natural history of BPH, a hormonal process influenced by testosterone, indicates the likelihood of gland regrowth. As such, complete embolization requiring no further treatment is unlikely, reinforcing the importance of keeping retreatment options open.
• To avoid complications, Dr. Mouli suggests embolizing from deep within the prostate and working back until the flow becomes static. This approach requires an in-depth understanding of the glandular anatomy and meticulous attention to embolization.
Table of Contents
(1) Standardizing Prostatic Artery Embolization: A Step Towards Consistent Outcomes
(2) Embolic Agents, Collaterals & Vasodilators in Prostatic Artery Embolization
(3) Advanced Techniques in Prostatic Artery Embolization
Standardizing Prostatic Artery Embolization: A Step Towards Consistent Outcomes
A consistent approach to prostatic artery embolization (PAE) could help to create reproducible outcomes and acceptance within the wider medical community. Variations in techniques, such as choice of catheters and wires, endpoints, particle sizes and use of coils or liquids lead to inconsistent data and outcomes. For instance, while smaller particles can lead to better infarction, they may increase off-target effects and risk of sexual dysfunction. To overcome these discrepancies, standard techniques from Brazilian and Portuguese studies suggest the use of 300 to 500-micron particles. Such standardization can lead to safer and more effective results with a more favorable side effect profile, making PAE comparable to other urologic therapies.
[Dr. Michael Barraza]
Sam, from just our email discussion, preparing for this, you had mentioned you feel pretty strongly about the fact that we need to have some sort of standardization in how PAE is performed. First, I completely agree with you and I think that is probably one of the barriers to making this grow faster is that people out there are doing this in different ways and we're still tweaking it. I just wanted to hear your take on it about where we stand in that process, and basically how long do we have until we feel confident about the best way to do this so that we can all be doing this in a similar manner.
[Dr. Sam Mouli]
I think everybody has a different flavor of doing it right now. I won't really speak to the radial versus femoral approach because I don't think that makes a huge difference in terms of the actual outcomes. It's just patient preference at that point, but what catheters and wires to use, what your endpoints should be, perfected or not perfected, what size particles, we should do coils, should use liquids, et cetera. Everybody's doing it a little bit differently. It's not reproducible and the data is not consistent. That's been the big knock from the urology standpoint.
When you look at a TURP or an Aquablation or any of these minimally invasive surgical therapies, they're all done pretty much exactly the same way. There isn't a lot of room for artistic interpretation, if you will, for these cases when the urologists do them. When they have these large series, like everybody's trained up and they're all doing it the same way, we need to approach PAE with the same rigor. I think the best way to do that is to follow the data. We have a lot of long-term data, as I mentioned, from the Brazilian and Portuguese groups as to what the best techniques are and how we should be doing them, and what size particles to use and the techniques.
We should be implementing all of that because that's our best long-term data. If everybody's doing it that way, I really feel strongly that we can get the numbers that we should be getting in all these cases and getting the outcomes that make it very comparable to urologic therapies and very consistent.
[Dr. Michael Barraza]
What do you think is the best means of educating, I don't want to say the public, but the IR community on really what this way is, the best way to do this moving forward? I mean, are we talking about, I don't really know the right way to inform everybody what they should be doing.
[Dr. Sam Mouli]
Yes, let's use this podcast and do it right here. Just being a little bit facetious, but the big studies that we have, all of them pretty much start off with data from 300 to 500-micron particles. My standpoint is everybody who's doing it, if you're going to do a de novo PAE, not a repeat treatment, not somebody who's already undergone surgical therapy and has a recurrence of symptoms, just a de novo, new PAE patient, all of the data points to 300 to 500, so that's what you should be using in those patients. Just stick to that. There's a lot of safety there.
It shows really good efficacy with a really, really favorable side effect profile. So why change any of that up? I think there's been isolated reports and it is what I've seen from my own experience is when you get a little bit smaller in the particles and when you're going down to the smaller size of like 1 to 300 or so, you certainly get a better infarction that is without question, but you start to get a few more off-target effects and more risk of sexual dysfunction. I think one of the big positives for PAE, you let a lot of patients respond to is the minimized risk of sexual dysfunction. Basically, no risk of sexual dysfunction if done.
[Dr. Michael Barraza]
Absolutely. One of our biggest selling points.
[Dr. Sam Mouli]
Exactly, exactly, exactly. What I've seen is when you use a really small particles, you basically infarct the center of the gland, maybe it peels off and you're basically done an endovascular resection of the prostate. Yes, it's a great response. They're going to prograde, but they're also going to have retrograde ejaculation, so do we really, really want that? I would argue no.
[Dr. Michael Barraza]
No, and is it even necessary that that extra level of infarction? We've seen the same thing with fibroids, try to go smaller. Is it necessary, you still get good results with 300 to 500?
[Dr. Sam Mouli]
Exactly. If we're really pushing safety and much more favorable side effect profile compared to the other options, I think it really is contingent upon using that kind of technique. I think that's one of the big ones because everybody's always feels a little bit differently about what size particles to use and that potpourri of flavors and stuff.
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Embolic Agents, Collaterals & Vasodilators in Prostatic Artery Embolization
Dr. Sam Mouli and Dr. Michael Barraza discuss the selection of embolic agents for prostatic artery embolization (PAE), emphasizing the typical use of 300-500-micron particles in routine practice. An exception can be made for retreatment cases after failed UroLift or GreenLight procedures, where smaller and more friable vessels may necessitate the use of different tools. In these cases, collaterals are more common, making it essential to avoid non-target embolization. They further discuss the management of collaterals that emerge during embolization, advocating for the upfront identification and handling of significant collaterals via cone beam imaging and vasodilator use, to create a low-pressure vascular bed in the prostate. The gradual and slow embolization, as a practical approach, ensures safer outcomes while reducing the need for multiple runs.
[Dr. Michael Barraza]
Okay, let's move on again. Let's talk about embolic agents to use for PAE. You had mentioned that you prefer 300 to 500-micron particles. That's what I'm using as well. Just for me, it's just that in coils, you hear about people using liquid and bollocks. You would mention that and smaller particles. Are there ever any circumstances where you're using either of those, anything smaller or liquid?
[Dr. Sam Mouli]
No, not really. Not after all the data that's been out there for smaller. Unless you have a patient that you're retreating for whatever reason or they've already undergone previous surgical therapy and then those vessels can get very dicey and they're very small. We've had good results in patients that we've retreated after UroLift failures or GreenLight failures or other things like that, but those vessels could be smaller and friable and thus require different tools. In those cases, the other thing that we've noted, and we'll be publishing this pretty soon, I think we shared it I guest last year, is those patients tend to have a lot more collaterals.
You have to be really vigilant about coiling and looking out for non-target embolization in those patients because after they've been resected or partially resected, what have you, the blood flow and vascular anatomy changes quite a bit.
[Dr. Michael Barraza]
That's interesting. I didn't realize that after UroLift, et cetera, they get more collaterals. I don't think I've had to retreat any of those. You mentioned that those arteries can be a lot more friable and presumably more torturous. How are you treating them differently?
[Dr. Sam Mouli]
All of the same tools we talked about with cone beam and everything like that. Aggressive with the vasodilators, very aggressive with coil embolization because we find collaterals to the penis, bladder, rectum, everything that you can imagine, they're going to be collaterals, basically. The vessels are usually much smaller and more wispy and friable. There's a lot more instead of a big single artery, there might be a lot of tiny little branches going to the tissues. It can be very challenging, but the patients do really well after the treatment. It's just a little bit more meticulous work is required to do it safely.
Very liberal with use of coils, very liberal with use of vasodilators, and getting a lot of good angiographic images to make sure that you're not hitting anything that you don't want to hit in the wrong target bed.
[Dr. Michael Barraza]
Let's talk a little bit more about collaterals. You've already told us what you do for the ones that you identify in cone beam CT that you embolize before going after the main arteries to the gland. Let's talk about how you approach the ones that pop up during your treatment, during embolization, the ones that you see when you do your run after. How do you decide which ones need to be embolized? What do you do if it's something you can't reach?
[Dr. Sam Mouli]
That's a great question. When I initially started out doing these, I would give a little bit of particles, 3 cc Medallion or something like that, then do a run a little bit more and then do a run. Probably the doses were way too high.
[Dr. Michael Barraza]
Mine are still there.
[Dr. Sam Mouli]
Yes. You're like, "Oh no, what do I do with that?" Exactly. Like, "Do I go after it? Where is it going? Is that going to the penis? Is it going to the bladder?" Getting a lot of anxiety from that. What I've found is I do the cone beam upfront. I identify what is hemodynamically significant, that it's lighting up as a collateral upfront before you've done anything, before you've changed the flow dynamics, take care of the ones that I need to take care of, get into the prostate, give a very liberal dose of nitro, something around 200 mics per side or more, followed by verapamil.
The verapamil idea is in line with some papers that have been written and also what's been reported with like balloon microcatheter experience in that if you create a low-pressure vascular bed in the prostate, any of the other vessels are like protective inflow. Instead of you injecting and then the contrast going out the collaterals or the flow going out the collaterals, now it's low pressure in the prostate, so the flow is coming in from everywhere.
As long as you embolize really slowly in that low-pressure state, you shouldn't see anything go out. I dilute my particles in 20 ccs of straight contrast and then I inject with a really big syringe. I'm forced to go really, really slow.
When I started out, it was hard to get into the prostatic artery and that was all the time in the case. Now it's like getting in, in five minutes, and then embolizing for 25 per side and just going really, really slow. Then as long as you don't see reflux distally from the catheter tip beyond the prostate, I don't do another run until it's static. It's worked out really well from that standpoint. I sleep at night better. It's a lot simpler.
[Dr. Michael Barraza]
Dude, just using 300 to 500-micron particles also helps me sleep a whole lot better knowing that a couple of those little guys are probably going to leak out there. It seems to be pretty well tolerated with 300 to 500-micron particles.
[Dr. Sam Mouli]
Exactly. All the cadaver studies and basic science studies in the space have shown, what is the vessel size of these different organs that you want to avoid, basically. As long as you're in that range, the likelihood of you damaging those other structures, as long as you don't directly inject the penis or the bladder or something like that very, very low. Just go real slow. The slow, steady embolization I found works really, really well. Then I don't have to do multiple runs in these patients and the outcomes are just as good as how we were doing it previously.
[Dr. Michael Barraza]
Man, that's super helpful. That's going to change how I approach these.
[Dr. Sam Mouli]
Take good pictures upfront and then just stop after that. Take your time with the embolization. It's much, much simpler.
[Dr. Michael Barraza]
Oh, it sounds like it. Certainly, that's one thing about my own performance it needs to change or my dose rates are pretty high. I think a lot of that comes from those runs in the middle. Yes, I look forward to making some adjustments. No need for perfected technique in your practice. I'm personally not advancing it any farther after I get there.
Advanced Techniques in Prostatic Artery Embolization
Dr. Sam Mouli and Dr. Michael Barraza also discuss best practices and considerations in prostatic artery embolization, highlighting the role of microcatheters, particles, and coiling. Dr. Mouli explains his preference for using 300 to 500-micron particles, advocating against coiling unless in specific circumstances like patients with hematuria. He warns about the limitations of coiling and the use of liquids, stressing that these techniques might prevent future retreatments, which could be necessary given BPH's nature as a hormonal process. Therefore, it's important to adopt an approach that considers long-term patient needs, specifically the potential necessity for retreatment.
[Dr. Sam Mouli]
Yes, so that's a good question. What were the end-points imperfected. You start proximal, then you go distal, if you've already taken it to stasis, how do you know when to stop? Some of the endpoints unperfected are like weird blush, vessel rupture, things I just don't really feel comfortable seeing on an angiogram. What I've done more recently and with this newer generation of microcatheters from Boston and Terumo and everybody is you can get really deep up front.
Then I just get as far as it wants to go and then basically start embolizing, then embolize all the way back until it's static up to where I think it's safe that there's not going to be any reflux anywhere. Get really deep as far as you can go up front and then just embolize.
[Dr. Michael Barraza]
You can take a true select almost in the gland.
[Dr. Sam Mouli]
I've taken it to the other side.
[Dr. Michael Barraza]
Wow. That's cool. After you do your embolization with the 300 to 500-micron particles, do you use gel foam or anything else or just particles and go?
[Dr. Sam Mouli]
Just particles and go typically. The only time I'm adding anything else is in the patients with hematuria or something like that, that are coming in because they're bleeding and they are having clot retention and things like that. I get more aggressive with either gel foam or more typically with coils. Because in those guys, a lot of times they're on blood thinners. They got to get back on them for their heart or what have you. I don't want them to ever, ever bleed again, and so that's when I'm "coiling out". Otherwise, I'm pretty anti-coiling out, which we can get into.
[Dr. Michael Barraza]
Let's get into that. Sam, I guess what I don't understand and it's not something that I do in my practice. Tell me the rationale for coiling out, I guess for our listeners. What is coiling?
[Dr. Sam Mouli]
I don't want to speak to it too much because I don't do it, but it's a technique in that you embolize the prostate to stasis and then you coil the parent vessel when you're done such that there's a better infarction, less perfusion to the gland, and more permanent embolization if you will. Now, is there a long-term data showing that that's the better way to do this? No. It hasn't happened yet. Maybe there will be, and maybe I'll be proven wrong. That's a possibility. I think if you take a more global view of BPH, BPH is a hormonal process. Its growth is because of testosterone, is stuff like that bloodstream, and we are not taking that away from patients, not with TURP, not with embolization, not with anything.
Really the only way to prevent regrowth of the gland is complete surgical removal with radical prostatectomy. Even with TURP, the natural history of the disease is such there's probably up to a 20% chance of recurrence at five years requiring either medical or surgical therapy. You know the gland's going to regrow, why not leave yourself an option to get back in and retreat because, on a long enough time scale, the patient will need retreatment?
I don't think you can ever get complete perfect embolization. That's never going to require treatment again. I think that's very unlikely, and so why not facilitate a retreatment in patients? Because I think if you ask a patient their options if they did really well with their first PAE and 5, 10 years later they need a second one, I think they would opt for that rather than going through a TURP or any other more invasive surgical therapy.
[Dr. Michael Barraza]
Personally, I guess I don't believe that the coil adds much to the embolization, at least not in the sense that it's going to cause much further gland infarction. When you think about it, half the time you're doing these patients have atherosclerotic stenosis and the vessel you're trying to treat and inflow, I don't really think so much as the issue. You're getting flow from all these other branches as well.
[Dr. Sam Mouli]
Exactly. I don't think it adds much and I think it only creates a difficulty if you have to go back in and retreat the patient. That being said, if they're coming for hematuria and they're bleeding, and you really want to make sure that they don't bleed again, especially if they have to go back on anticoagulation. Those patients, I will coil the parent vessel.
To the same end, that's why I don't really think there's a really good role or justification for liquids in this space. Because if you think about it, a liquid is very similar in the way it works to a coil and you're just really occluding the main branches, you're pretty much guaranteeing that you're never going to be able to retreat this patient. When we know that the natural history of the disease is such that they will likely require retreatment at some point, and so why do that and not be able to offer this therapy again to the patient if it's so advantageous from a safety and side effect profile?
[Dr. Michael Barraza]
Totally. It's more proximal embolization than particles. For me, I don't have a role for it.
Podcast Contributors
Dr. Sam Mouli
Dr. Samdeep Mouli is an Assistant Professor of Vascular and Interventional Radiology at Northwestern University Feinberg School of Medicine.
Dr. Michael Barraza
Dr. Michael Barraza is a practicing interventional radiologist (and all around great guy) with Radiology Associates in Baton Rouge, LA.
Cite This Podcast
BackTable, LLC (Producer). (2023, January 9). Ep. 280 – Current Controversies in Prostatic Artery Embolization [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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