Advancing Pelvic Sarcoma Reconstruction with 3D Printing

Podcast Transcript

Dale Shepard, MD, PhD: Cancer Advances, a Cleveland Clinic podcast for medical professionals exploring the latest innovative research and clinical advances in the field of oncology.

Thank you for joining us for another episode of Cancer Advances. I'm your host Dr. Dale Sheppard, a Medical Oncologist, Director of International Programs for the Cancer Institute at Cleveland Clinic and Co-Director of the Cleveland Clinic Sarcoma Program. Today I'm happy to be joined by Dr. Luke Nystrom, an Orthopaedic Surgeon and a Co-Director of the Sarcoma Program. He's joined us previously to talk about management of soft tissue sarcoma in adults, and that episode is still available. He's here today to discuss custom 3D printed reconstruction of pelvic sarcoma defects and complex reconstructions. So welcome back Luke.

Lukas Nystrom, MD: Thanks for having me.

Dale Shepard, MD, PhD: It's always nice to get some sarcoma discussions here.

Lukas Nystrom, MD: Yeah, yeah. It's near and dear to both of our hearts, so that's great.

Dale Shepard, MD, PhD: Give us a little bit of an idea of what all you do here at the clinic.

Lukas Nystrom, MD: Yeah, so I'm an orthopaedic oncology surgeon that pretty well confines me to doing sarcoma and a metastatic bone disease in the extremities. And the pelvis is one of those areas that would still be considered the extremity for these purposes. And so that is very much our territory, but anything in the arms, legs, pelvis related to cancer is pretty much I'm your guy as well as my partners.

Dale Shepard, MD, PhD: When we think about these tumors that involve the pelvis, what kind of volumes are we thinking here? How many patients on average?

Lukas Nystrom, MD: It's fortunately a pretty low number for the patient's sake 'cause it can be a very difficult problem. But in general, I'd say we see one to two of these patients per month in our group. So it's a fairly low volume.

Dale Shepard, MD, PhD: We're going to be talking about defects in the pelvis. And how often does this occur because of cancer compared to other causes?

Lukas Nystrom, MD: Oh, that's a great question. It's much more common to be seen with other causes. So we do a lot of joint replacement here in the orthopaedic department at Cleveland Clinic and as a sequelae of joint replacement surgery, when those parts come loose, they can oftentimes leave a defect in the pelvis. So this is something that's familiar to a lot of my partners as well, but for very different reasons. Fortunately, the cancer side of things is relatively low and that volume I referred to before was referring to cancer specifically, but it's a well-known issue in the orthopaedic world.

Dale Shepard, MD, PhD: When we think about issues that come about in terms of reconstructions, how are cancer surgeries? What sets those apart from other reasons to have a defect in the pelvis?

Lukas Nystrom, MD: Yeah, probably the biggest one I could think of is that our goals of the surgery are obviously quite different. We're trying to get a negative margin around a tumor typically, and so we make bigger defects. So I think the biggest thing that would set them apart is the defects are much larger. But on the flip side of that or the plus side is we control what the defect looks like. So a lot of my partners don't have that benefit. When a prosthesis comes loose, it'll kind of wear out the bone however it wants to or if it gets infected, they'll have an infection that does whatever it's going to do, but we make the defect. And so that is one of the benefits and I think pertinent to what we're talking about today.

Dale Shepard, MD, PhD: We're going to talk about these 3D printed reconstructions. Before that, if you're not using that, what are traditional means to fix these? So what are we replacing by doing 3D reconstruction?

Lukas Nystrom, MD: Yeah, and I should say that the 3D reconstruction is actually in our world is somewhat of a controversial thing. So historically what would be done is you would remove the pelvic tumor in one of two ways. One would be something called an external hemipelvectomy where you actually remove the leg along with the pelvis tumor, and that's still necessary sometimes. So it's not as if we've made that issue go away with these 3D implants.

And then the other way is something called an internal hemipelvectomy where you remove the pelvic bone tumor but you keep the leg. And historically and still very commonly performed today is a procedure where you sort of reattach the soft tissue and keep the leg sort of suspended by the soft tissue to the remaining pelvic structures or the abdominal wall, and it kind of scars in there and people can have some function still, but the goal with what we're trying to do with these 3D reconstructions is to improve the function, see if we can make it even better.

Dale Shepard, MD, PhD: We're going to talk about various things related to that, but just so we don't miss out on the fun part, you mentioned that there's some controversy. What does that center around?

Lukas Nystrom, MD: It centers around the fact that when you do a 3D reconstruction of the pelvis, you're increasing the risk of complications pretty substantially. We're putting a large foreign body into the human and we are also increasing the length of the surgery by that reconstruction. And those who don't perform this would argue that the function of those who aren't reconstructed in this way is actually quite good.

I would counter that by saying our methods of measuring function have not been optimal, and so there's a pretty low ceiling effect on the way that we measure function after oncology surgery. So those are the sides of the argument though.

Dale Shepard, MD, PhD: You mentioned the external hemipelvectomies, and a lot of that is based on where the tumor is located in the pelvis. Are there areas of the pelvis, are there certain reconstructions where it's clearly better than others?

Lukas Nystrom, MD: Yeah, that's a great point. In order to be able to do this successfully or the optimal candidate, somebody for a 3D reconstruction would have some substantial remaining amount of bone on one or both sides of the pelvis to or of that same side of the pelvic ring in order to secure a prosthesis. So that's part of it. But we also have to make sure that we're preserving blood flow to the leg. Obviously, nerve function to the leg has to be preserved. We have to be able to safely save those nerves. And we have to keep in mind that when we do these techniques, we can't compromise our first priority, which is safe oncology treatment, removing the tumor completely. So all of those things have to sort of align for this to be a good idea for a patient. And there are times when I've seen several in the past year where we've decided that not reconstructing with a 3D reconstruction is the best option, so we still use those tried and true historical techniques.

Dale Shepard, MD, PhD: I guess before we get too far afield, when we talk about 3D reconstruction, what exactly goes into that?

Lukas Nystrom, MD: There's two elements that really go into it. The first is the resection part of it, which we actually still use some 3D printing techniques for which I can explain. But the actual 3D reconstruction is creating a piece of metal that is designed exactly to fit the defect that we created by removing the tumor. And so we can essentially restore that pelvic bone with a piece of metal that's customized to the patient after the tumor removal.

Leading up to that, we will oftentimes and most frequently create 3D printed custom cutting guides to safely navigate ourselves around the tumor to make that exact defect that we're going to try to fill with this implant. So it's a two-step process.

Dale Shepard, MD, PhD: With the introduction of 3D print and using the cutting guides reconstructions, what's the effect on removing the tumor itself? And I guess what I'm asking is do you have smaller defects because you know exactly where you're cutting and exactly what you're going to refill in, or do you have the luxury of doing a little bit of a wider margin because you know that you can have something to fit in there that's going to kind of match up to the defect?

Lukas Nystrom, MD: Yeah, that's a really nuanced question, and we walk that line all the time. I would say we go as wide around the tumor as we can when we know we have a little bit of extra room to play with. We still get nervous about getting too close to the tumor because there's a lot of trust that goes play when you create these guides to get around it.

Number one, do you have the guide in the exact right position? Because although it would seem fairly straightforward when you're doing it during the surgery and there's soft tissue blocking access to various parts of the skeleton, it can be a little bit tricky to make sure that you're situated exactly where you want it to be. So we like to leave ourselves a little bit of a wiggle room to make sure we're not getting too close on that margin.

The second part is that the processing time of creating a guide currently in 2024 requires a little bit of time. We can get that time down to about two weeks, which is great, but a lot of times we're doing that much farther upfront trying to fit it into a time when there's going to be a window in chemotherapy, for example. And we're trusting that the tumor at the time of surgery looks the same as it did at the time of planning the guides. And so that is also a bit of a leap of faith in some situations, and we like to leave some margin for error there.

But we will walk that line, and we'll do it even simultaneously in the same patient. So, we'll get farther away from it when we know that it doesn't really matter from a functional standpoint, and we'll get closer to it when we know that we either have to or it's going to significantly impact the function. But again, never wanting to compromise the margin and the oncologic goal of the surgery.

Dale Shepard, MD, PhD: So certainly, from a surgical perspective, there's that time that's built in that is needed to do the implant from a surgical procedure standpoint, any increased time during the surgery?

Lukas Nystrom, MD: Yeah, there's push-pull there actually, because the use of the custom guides I think decreases our surgical time. It makes the whole process of getting the tumor out much more efficient and much quicker. The reconstruction part is much longer. It adds at least an hour to two of surgical time, in my opinion, for putting that in securely and safely and making sure it's stable and all of those things that we care about.

Dale Shepard, MD, PhD: From a resource standpoint, I mean, is this something that is primarily only done at large centers or how widely adapted is this use of 3D sort of imprinted?

Lukas Nystrom, MD: Yeah, so there's two different sides to that question. One is 3D printing in orthopaedic implants has become very, very common. It's almost uniform that all companies will 3D print some surface on the back of their implant to allow for bone-in growth, and that has been very, very effective 'cause they can 3D print a surface that mirrors cancellous bone essentially. So that has been widespread.

Now the use of 3D printed implants for the purposes of fitting a specific shape of defect, that is something that I would venture to say is done primarily at large centers or at least high-volume centers. So not super common.

Dale Shepard, MD, PhD: Are there particular patients when they come in, you see a defect, you see something that's need to come out? Are we at a point where you can kind of clearly look and say that's clearly going to benefit from a 3D printed implant, or is there some variability in that?

Lukas Nystrom, MD: There's definitely some variability. I would say there are shapes and anatomic features of tumors that make it seem like a very attractive idea. We don't have the data yet to support the fact that it's clearly superior, and that's something that's ongoing not only at our center, but multiple different centers. And we're part of a collaborative group that's looking at that.

Patient factors are a big deal. For example, risk factors of infection are something that we look at very, very significantly, as well as baseline activity level. We want to use this technology because it does come at increased risk of complications, but also cost and to somebody that it's very likely to be beneficial. And again, the big drawback of this technique is that infection is one of the risks we worry about the most. So we want to be very careful about doing it in people who have poorly controlled diabetes, obesity, other factors that you might typically associate with increased risk of infection.

Dale Shepard, MD, PhD: When we think about an infection, I guess the question is, is the infection risk 'cause you mentioned that two or three times, is it higher with 3D printed implants than it is say with joints and prosthesis? And is it because of the materials that are used or is it kind of equivalent?

Lukas Nystrom, MD: No, it's a great question. It's I would say fairly equivalent. The issue with doing it in big pelvic reconstruction cancer surgeries is that we're adding it onto the back end of a surgery that's probably already taken in the range of four to six hours. And we know that that time that the patient is open is one of the big factors that correlates with infection. So, we're taking it in essentially somebody who's been open much longer than a typical joint replacement. Then we're putting in a larger piece of metal than usual. And so you got to be very careful.

Dale Shepard, MD, PhD: What about coverage? Always think about insurance coverage, and is this something that is, you say it's not necessarily been shown to be better than other techniques, but is it something that's widely covered by insurance?

Lukas Nystrom, MD: Yeah, that has not been a typical issue that we face. I think most payers can understand very similar to how we do in the extremity, distal femur, proximal tibia, things like that where you're removing a large piece of bone and we're doing our best to reconstruct it to optimize function. That hasn't been a big issue.

Dale Shepard, MD, PhD: When we think about surgeries, the natural thing is it's rare to see a surgeon that doesn't want to try to make things better, either faster or better outcomes from a performance standpoint or something. So, what are the things that are sort of in the works to make this process better?

Lukas Nystrom, MD: Oh, to improve how we do-

Dale Shepard, MD, PhD: To improve either outcomes or surgical times, techniques?

Lukas Nystrom, MD: Yeah, great. So, I think one of the things that we can really improve a lot is the time it takes to manufacture. And certainly, that's something we do with our partners in industry and they're working through those.

One of the things that has been attractive, and I think people are pursuing is, is there a way that we can take what we're doing in this custom pelvis world and make an off-the-shelf option? And so that's one big step that we're trying to take.

Another is can we improve the way that we move these things through the system? Currently, there's one company now that has FDA approval for this process to create a custom pelvis for this defect, but that's the only company that does. And can we find ways to make the process of creating a 3D implant more streamlined?

And then lastly, as in many other surgical subspecialties, robotics has become a huge part of orthopaedic surgery. And can we marry this technology with our capabilities in robotic surgery to make the 3D guide part unnecessary? So we have robots that can now essentially assist us with the plane of our cuts. The benefit of that is it would allow us to change things real time if we decided we need to because of a margin concern or what-have-you. So those are, I think, probably the lowest hanging fruit that we have.

Dale Shepard, MD, PhD: And we've been talking about reconstructions in the pelvis. How has the 3D printed implants affected your other surgeries in terms of extremities?

Lukas Nystrom, MD: Yeah. It's been great because we have the opportunity or the ability rather to get a little bit more creative with sparing critical portions of bone. Some surgeries are pretty straightforward. Like osteosarcoma of the distal femur, it's a pretty good surgery where you remove the end of the femur and replace it with an off-the-shelf implant. But other areas, proximal femur, proximal tibia, we can save pretty vital bone attachments and create a custom 3D printed implant that will fit that defect exactly. So, it's found its way into pretty much all aspects of extremity surgery.

Dale Shepard, MD, PhD: You talked a little bit about some patients that may not be good candidates, some areas that might be an advantage. Is there a risk this gets overused?

Lukas Nystrom, MD: I think that's always a concern. It's a new technology and it's attractive to surgeons for what the potentials of it are, but it comes at a cost, and I personally do worry about it stressing the system if it were to become overused. So, we have to find a way to drive down costs and make sure we're using the technology appropriately.

Dale Shepard, MD, PhD: Well, it sounds like certainly some interesting things you guys are developing and helping patients and appreciate your insights.

Lukas Nystrom, MD: Yeah, no, it's a pleasure to be here. Thanks for having me back. Look forward to the next time already.

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