Rectal Spacer Placement in Prostate Cancer: A Procedural Guide

[Dr. Juan Javier-Desloges]:
There's two gels out there now. As we all know, there have been two trials that have been-- The most recent one published with bare gel and SVRT patients, and then the older trial from Boston Scientific for spacer looking at IMRT patients. They've both shown benefits in terms of rectal toxicity, but the gels they're different. I think it's a little nuanced to anybody that's getting into rectal spacing. I was hoping that we could maybe talk about both and what their differences is and you could maybe add to what I have to say. For Boston Scientific, the SpaceOAR gel, it's visible on CT, it's not visible on ultrasound. Once you place the gel, it blocks out the prostate, so you can't see that well. You do a hydro dissection prior to spacer placement, which I believe is an advantage because I have had a number of patients that just do not have a lot of pararectal fat. We didn't really get into placement of the gel and the needle position at all.

Generally, when you try to put these gels in, you take the needle from an anterior approach, to come down towards the pararectal fat plane. If you've done a prostatectomy, you know that just some patients don't have much pararectal fat. You're right on the rectum sometimes. The same is true when you're doing an ultrasound. I don't really feel that this is a learning curve issue, but rather an anatomy issue. You need that sometimes hydro dissection to spread apart that area and make sure that you are placing the gel in the right area because you can get it into the navigated fascia, you can get it into the prostate, you can get it into the rectal wall. While none of that has happened to me personally, I do feel that leaning on the hydro dissection has prevented that.

The other major difference is, for SpaceOAR, you're a little bit under a time crunch, which is good or bad, depending on how you look at it. You want to get the gel in and you want to get that patient a radiation usually pretty quickly. The way that our protocol here works is we put patients on hormone therapy for six to eight weeks, and then they'll get the SpaceOAR gel. Then usually within a week after that, they'll get their sim and then they'll get their radiation. I think it's controversial whether or not you really necessarily need to give anybody ADT prior to radiation or when you start it. I think from a scheduling perspective because we just have so many patients. I don't think it matters if they get it when they start ADT or when they're six to eight weeks in, but that has been the general protocol that we've followed.

For Barrigel, the major benefit I think is it's visible on ultrasound and it also lasts longer. There have been concerns raised about how long does it actually last. In the trial, there were a number of patients that I think had absorption times beyond nine months or even 12 months, but majority absorbed within nine months. Now we do know that the gel is safe. I think it's pretty popular for lip filler. I think that's where they got most of their safety data. That longer time, if there's a misplacement of the gel, I'm not sure how I would mitigate it, but would like to get your thoughts on the differences between the two.

[Dr. Neil Taunk]:
Juan, you've really nailed the highlights of what they are. Some additional differences regarding the products, they have very different setups. SpaceOAR from Boston Scientific requires a multi-step process where you have to mix a powder vial into a powder gel into a liquid and then they mix that all around to essentially create the hydrogel versus Barrigel, now part of Teleflex, comes pre-packaged in single-use syringes, ready to use. There's no mixing and they're stable. The setup time is different.

There's a little bit of preparation with SpaceOAR versus Barrigel, you can use right out of the box. I did make the point regarding injecting say all of it at once with SpaceOAR could be good and bad. Some of our doctors like when they place it, you place it over 10 to 30 seconds, whatever you choose to do. There's different ways to apply it. It's done. It's over. if you've hydro-dissected, you've created the pocket effectively, which I also agree with you is a really nice safety check to have, to know that you are in fact in the right space, and gives you an out to abort that procedure. If you're not in the right space, you put in the gel, and then the whole thing is done.

Barrigel, you do have to be a lot more thoughtful in terms of where you put the gel and then where you reposition the needle. There's a lot more repositioning required. Our more experienced users tend to be more successful because they're just so much more savvy at moving the needle around where they want it to go. On the whole, I can't really say that one is significantly faster than the other. You borrowed time from one aspect of it and maybe just put it in another aspect of the procedure. Really, our turnover time is the thing that dictates most all of it. The safety data for the NASHA that's used in Barrigel, yes, did mostly come from lip filler products. These products are used all over the body already and get very impressive long-term safety data for this. There is also a similar product that the company has, which is specifically used to bulk the rectum for patients with say, fecal incontinence. Deliberately placing this NASHA product into the rectum. Now, granted, those patients were not treated with radiation, so we can't necessarily infer that it's safe to radiate when that stuff is inside the rectum.

SpaceOAR will take around six months fairly consistently to go. I think reliably we say we have about 12 weeks of stability. There is a bit of time. We place it basically right before we want the radiation to happen. Say during the COVID-19 pandemic, patients who had spacers placed and then our clinic shut down, we kept them on ADT because we weren't treating non-emergent patients with prostate radiation for a while. Some patients we either did another procedure on or they just went ahead and did their treatment even after the gel resorbed. The Barrigel is supposed to resorb I think mostly within six to nine months, but there are data suggesting that you will still have gel at 12 to 18 months afterwards. There is a reversibility aspect of Barrigel that is offered. You would use hyaluronidase to do that, but I think the experience is very limited and there would be a fair amount of counseling to be done to tell a patient, "Hey, it wasn't in the right place, but we need to do another procedure to reverse it and then maybe fix it." I don't really have a good grip on how widely it's done, except I think I've just heard about a single case of it really. That's another potential aspect of it, but you hope you just do it right the first time so you never have to go back.

[Dr. Juan Javier-Desloges]:
Yes. I think this is one of the things that goes back into the pre-op counseling session I tell patients about. In urology, we do a lot of different types of implants. We do penile implants, we do prosthesis of the testicle, AUS, and if those devices get infected or if they're misplaced, we can take them out. You can't really do that with the gel. The gel becomes this amorphous material within the peri-rectal space and it is not whether you're injecting something into it to dissolve it or you're trying to suction it out. It's just not possible. Once it's in there, it's in there. It's not coming out. You just got to wait until it absorbs. Going back all the way to when I was a trainee and we first started doing these, there were some patients that had infiltration of the rectal wall, and the guidance at that time, and I haven't seen it in a while, has been just to wait for about three to four months before offering them radiation. Is that generally what you've done when that does happen?

[Dr. Neil Taunk]:
Yes. The management of patients who have a suboptimal placement is very imperfect and very heterogeneous. In the original trial, I believe 7% of patients on a post-hoc analysis had some degree of rectal wall infiltration using the SpaceOAR Classic. The SpaceOAR Vue and SpaceOAR Classic, neither of them are particularly visible in ultrasound, but the SpaceOAR Vue is what we prefer at Penn. That is available on CT. All these patients had an MRI in the original study because that's what was required. I think 7% had rectal wall infiltration, but there was no high-grade subsequent toxicities that were experienced by these patients. In terms of how we tend to manage it is most of our patients that are treated at our main campus, we have a distributed model. We have around 60 doctors in our radiation oncology practice spread across our various sites. In these patients, the ones that are treated at the main campus, they all get an MRI anyway. We do have that to reference.

Patients with minor infiltrations, which is really just the superficial layers of the rectum, we'll go ahead and we'll continue to treat without issue. Any patients with say any deep infiltration deeper into the submucosa or we've seen some patients from outside that have had gel placements that have even intraluminal gel, we absolutely will not treat. There's some thought to say that if you say, do an anoscopy and check if there's no gel in the lumen, you can proceed forward. It's hard to say if that's correctly the data-driven approach. If there is a sufficient amount of physician worry, I think it's reasonable to wait. Most patients can comfortably wait for prostate cancer treatment, particularly if they're on ADT. Superficial infiltrations, if we see it, we're generally comfortable proceeding forward with it. Again, we take a nuanced look and make sure to look carefully. That's only just a little bit. How do you guys manage these and your practice?

[Dr. Juan Javier-Desloges]:
Again, we don't do 200 a year. We probably do about 70. We just haven't had one. I actually was just taking notes here with my microphone on mute on how you are managing the rectum because I know it's bound to happen. going back to the way that we talked about how the gel is placed. if there's just not a giving periorectal flat pad, even if you follow all the maneuvers, sometimes you get a little bit of superficial infiltration. It's just not something you could avoid.