Advancing Patient Comfort- Maskless Head and Neck Radiation Therapy with Surface Guided Radiation Therapy

I’ll be talking today about one of our trials that we’ve started recently about maskless head and neck treatments.

Our disclosures are: we’re a center of excellence for AlignRT, for Vision RT, but none of that is reflected here. It’s all independent research and no financial motivation. So, as you all know a little bit about Central Florida and AdventHealth in Central Florida, Central Florida is awesome. Look at all the many fun things that we can do. But we have about 15 radiation oncology centers, 25 LINACs, two Halcyons, one gamma knife, three HDRs, 12 AlignRT systems—and I think that number is just growing thanks to Kenny—and two Invor systems, three SimRT systems, and currently just one MapRT and one DosRT.

One of our sites in Celebration here has the complete workflow from simulation all the way to treatment and treatment verification, and I think it revolutionizes our workflows. Some of it we’ll see in this talk, and some of it you’ll see in other talks from Mike and Anton on how we implemented SGRT in every step of the workflow.

But coming back to our topic, treating head and necks is difficult. Part of the difficulty comes from the anxiety. Mask anxiety is a big problem, and a few of the papers that I looked at quickly said that 43% of patients report significant anxiety before the mask fitting. So, you take them into simulation, they see that big thing that’s going to go on their face, and that’s kind of where the panic starts. Twenty-six percent of the head and neck patients report mask anxiety during and before, and you have a range of 14% to 58% of head and neck treatments that experience some sort of level of mask issues to the patient.

And how does that impact us? You can get treatment interruptions because the patient can’t handle it and needs a break, so you have to take off the mask, extend your treatment time, give them a break, put the mask back on, and try to continue, which interrupts the patient and could cause delays either in delivery of that fraction or even delays of the full fraction. Some of them will abandon treatment midway or not even start. It’s really a reduction of quality of life during their treatment; they’re already battling a terrible disease, and we’re just adding more complexity and suffering. Some of us have to rely on anxiety medication and other stuff—again, an unnecessary barrier to cross.

The traditional approach that most clinics probably use is a closed-face five-point head and shoulder mask. It’s a thermoplastic mask; it’s rigid. It gives you a very reproducible setup but introduces a lot of anxiety and claustrophobia, and you cannot use SGRT on that treatment—you’d have no valuable surface there.

Alternatives have come as SGRT became more popular in the form of an open-face mask. There are two versions: I’m showing a three-point mask here, but you can also get the shoulder one, so it’s a five-point mask with an open face. That improves mask tolerance in a sense that the patient can tolerate it more. It enables SGRT monitoring, yet you have a very small real estate volume there. It still confines your face—your mouth is really close to your nose—and it could still confine your breathing. But it has comparable accuracy to a closed-face mask, so the reproducibility is still pretty good.

The proposed approach is a fully maskless treatment and SGRT implementation—a full contactlessly experience. You can use six-degree-of-freedom monitoring using SGRT. You get only dorsal shell support, so only the bottom of the neck and head is supported. And you can add automatic beam hold: if you set a tolerance and the patient exceeds that, it will automatically hold the beam for you.

Our key study question is: can we eliminate rigid facial immobilization without compromising accuracy and patient safety? So to enable that, we have to think about a few things. We need surface tracking. We need a modality that can track six degrees of motion in the patient during setup—because we need an accurate setup—and during delivery. We need something to continuously monitor the patient; if the patient is going to move during treatment even slightly, we need something to tell us. When it tells us, we don’t want a delayed reaction; we want something to automatically hold that beam. And with all that, we want to enable that contactless, free experience.

The way to do it is to go from that traditional approach all the way to the SGRT approach. This dorsal shell experience—and I’ll tell you what we’re using—is just one example. Mike Thalhammer in AdventHealth Denver uses just an AccuForm for the shoulders and the head to basically produce that. So whatever kind of works for you, you can customize your SGRT workflow to do a maskless head and neck like that. That’s the flexibility and advantage of using an SGRT system.

Our objectives were to look at four things. We wanted to look at interfractional accuracy: determine whether the maskless workflow, using SGRT, maintained sub-millimeter interfractional accuracy or close to it. We were going to use SGRT versus IGRT validation, looking at SGRT measurements throughout the fraction, comparing our imaging to it, and seeing if they agree. We wanted to see if it made our workflow better, the same, or worse; did it take us longer to treat that patient, or was it smooth as if they were masked? And patient comfort is key here—a metric that is hard to do, especially if they did not choose the masked approach, but an assessment of how they feel and how they’re doing is important.

The patient selection criteria were set early on. We were obviously looking for head and neck patients suitable for conventional fractions who were able to maintain head stability, willing to participate, and approved by the physician. We don’t want people with head tremors or cognitive impairment where they can’t listen to directions. I kept my options open if they really preferred a mask, but for the 10 patients that we had in the study, we showed them both options, and they all picked the maskless option.

I will say that when I pitched this project to our head and neck physician and explained that I wanted someone who could follow directions and stay still, he came back with a list of patients who all had claustrophobia and anxiety. They were the opposite of what I asked for, but that’s how it is because those are the patients that need this workflow the most. It’s a blessing in disguise; if we can prove that this works in that cohort, then the other cohort will be easy.

Our general setup strategy: we used the Macromedics DSPS Prominent Dorsal Shell for our immobilization. We set them up using AlignRT and postural video, and then CBCT. We monitored them again with AlignRT with three degrees of motion. Our internal thresholds were set to two millimeters and two degrees. We did a post-CBCT verification for residual displacement—on some patients daily, on some weekly. We did our evaluation comparing what we saw in SGRT to what we saw on IGRT and plus more.

ROI selection was trickier because we needed something to mimic a mask so we could monitor the patient, so we came up with a three-tier ROI system. We started with four, narrowed it down to three: shoulders, face, and a treatment ROI. The reason why we have a separate shoulder ROI is because the rotation axis of your body is a different axis of rotation for your shoulders and neck than your face. We set them up to the bigger ROI, switch to the little ROI for fine-tuning, then go back to the big one to make sure it looks good, then switch to the treatment ROI, and treat.

We knew patients like to track the gantry with their eyes or blink or lick their lips, but it was never a problem in a masked workflow; now it is a big problem, so we’ve learned to cut that out. We exclude the lips and eyes because we’re not confined by a mask anymore. We have a lot more real estate, so we can expand it and exclude the stuff we know they’re going to move. We just have to keep in mind to add enough lateral ROI so during the arc delivery, both cameras can detect motion in six degrees.

Our results: we have a mean interfraction translation of one millimeter throughout all our translational axes and 0.9 degrees throughout our rotation axes. Our residual translation for post-CBCT was about half a millimeter, so we know they did not move from initial to post-CBCT. We had about 10% of patients with at least one threshold violation, but only 4% required repositioning. The maskless workflow actually proved to be more rigid because patients were less irritated and moved less.

Patient experience was 100% positive; none of them said they would want to be treated with a mask. Threshold violations are more frequent with maskless because of that freedom, but AlignRT covers us. Regarding treatment interruptions: again, more with maskless, but easily rectified. None of these cases were treated over our normal 15-minute time slot.

Because we have DoseRT and Cherenkov imaging on site, I’ll slide in this slide for fun: on your left is a surface dose from Eclipse, and on the right is the patient being treated. There’s no mask; he’s just laying there in his dorsal shell, closing his eyes, concentrating on staying still. We see the dose went where it’s supposed to go—it’s another form of verification.

Looking at a patient’s journey: one patient with a tonsillar malignancy, 70 Gy, 33 fractions. He lays on the dorsal shell, and we carve it around his shoulders and neck. The DSPS system can come in two ways: it can be a clip-on to your normal S-frame, or a standalone board. Our absorption studies on the additional carbon fiber frame showed it’s insignificant. After we created the VMAT plan, set up the patient, and got the real-time deltas green, postural video served as our virtual mask to ensure shoulders and head were in the correct place.

One statistic I wanted to finish with: we’ve had patients who said they would rather die than be treated in a mask. Our first patient was so scared he didn’t even want to get scanned in the CT. Since he was the first, I was present for most of his fractions, and you could see him after the first week—he would jump on that table and was happy as a clam. At the end, he basically said we saved his life because he wouldn’t have been able to be treated otherwise.

To wrap everything up: it’s clinically feasible—actually, it’s amazing—to treat with an open-face mask using AlignRT. You have active safety delivery with automatic beam hold. You get millimeter accuracy and a universal patient experience; we can offer this to anybody, claustrophobic or not. For the patients, it’s a super valuable addition to our tool chest. For our therapists, I didn’t change their workflow one bit. The physics part requires some commissioning work and validation to maintain that high level of accuracy, but other than that, it’s not too much. I have to say thank you to Mike and my team at Celebration for helping. Thank you all.

 

 

*This transcript has been AI-generated. Contact us at secretary@sgrt.org if there are any issues.