Clinical Experience with Non-coplanar Treatments

Kiran Kumar (00:01):

So I am going to talk a little bit about something he touched upon, which is non-coplanar treatments, and specifically, from a clinician’s standpoint, when we think these are valuable how we can make a difference in patient care. And so see if I get this to work. Perfect.

Kiran Kumar (00:21):

So here’s kind of the basic outline for the next 15 minutes or so that I’ll be talking. And so I’m going to start off just talking a little bit about, you know, what Noncoplanar is and why we consider it. But I really think, at least from a physician’s standpoint, it’s most powerful to just go through some cases. I’ll talk about the literature and some of the studies that are published showing which cases benefit from Noncoplanar treatments, and then go through some illustrative examples. And then I’d like to end on, you know, kind of some of the reasons that we often don’t do Noncoplanar.

Kiran Kumar (00:51):

And so, you know, I think I’m talking to a room of physicists and therapists and a lot of people who know this much better than I do. But just in case you’re not familiar with what Noncoplanar treatments are. So Noncoplanar treatments use a number of fixed or rotating beams that don’t share the same geometric plane, right? And so the goal of this is all to reduce beam overlap away from the tumor. And this is something that, you know, we were doing a lot of but then as you know, arc therapy came along and VMAT, you know, these plans became pretty good without Noncoplanar treatments. And a lot of physicians and a lot of radiation oncology centers have kind of moved away due to some of the barriers, which I’ll talk about at the end.

Kiran Kumar (01:34):

But I think it’s kind of unfortunate because as you know, from the MD standpoint, you know, what I would encourage everyone is to not just do pretty good treatments, but try to do the best treatment for your patients. And there are a lot of times that you’ll see where using Noncoplanar, like a simple thing by adding one, you know Noncoplanar arc, for example, could make a dramatic difference in the plan quality could significantly reduce the dose to OARs and have a meaningful impact in the patient’s quality of life. And so I think now we have new technologies like MapRT, which you’re hearing about that make this a lot easier. There are new Linac that have come out now that allow automated motion. And so I think we’re going to see a big renewal from the community in using Noncoplanar treatments.

Kiran Kumar (02:21):

And so the big theme that you’ll hear about for me is, you know, Noncoplanar treatments are really allowing us to reduce the dose to nearby OARs not in every case, but there are a lot of cases where this makes a huge difference. And so I think most of us are familiar using this in SRS or SABR or SBRT but there are actually a lot of other situations where it could be significantly beneficial.

Kiran Kumar (02:50):

And so I’m going to go through I’m not going to touch on all the disease sites, but I’m kind of going to highlight some of the most common disease sites that we are using Noncoplanar treatments in. So head and neck is what I’m going to start with. And we are using it both for conventional and SABR head and neck treatments. Not every single one, but there are certain ones that will benefit. And so here’s a very interesting study that showed they kind of compared coplanar VMAT, Noncoplanar VMAT and found significant reduction to many OARs. And if you treat head and neck cancer and some of these numbers are dramatic. And so there was, you know, a three grade difference in parotid, a mean a four grade difference in larynx, a mean of five grade to the oral cavity and pharynx. These are really big numbers in the head and neck world. And they did some modeling that shows up to a two third decrease in normal tissue complication and a 25% potential decrease in local recurrence due to dose escalation that using Noncoplanar treatments can do.

Kiran Kumar (03:50):

Nd here’s another study. This was actually a prospective, it’s a small study. It’s a prospective phase two clinical trial of 15 patients who had recurrent head and neck cancer. So here’s one of the cases where we’re very stressed about the dose to OAR in these recurrent settings. And in all 15 of these patients, they actually had a coplanar plan, a noncoplanar plan, and the noncoplanar plan was chosen in every single one. And it found significantly improved dose conformity as well as a significant reduction in dose to these OAR. And I think you can just see this image on the top right kind of the difference in this dose that’s falling to the contralateral side of the tongue. The things that we care a lot about in terms of side effects.

Kiran Kumar (04:34):

Here’s a case that we treated at UT Southwestern. And this was a right posterior ethmoid neuroendocrine carcinoma. And on the left you’ll actually see this was initially started on our unity, which is our adaptive Mr. Linac. And so one of the things that, you know, at UT Southwestern, we’re very lucky, and I have a lot of our physicists here we have a lot of technology, right? We have a lot of toys to play with. And so we have these MR Linac’s we have our Ethos, our CT guided adaptive Linac, and this was attempted to be true on the Unity, but unfortunately, with some of these machines, right? You’re, you’re confined to coplanar treatments. And this was a patient of David Sheer, who’s the head of our head and neck, and he ended up switching off this due to the plan quality.

Kiran Kumar (05:21):

And you can see on the top left just how much dose is spreading left and right for this ethmoid sinus cancer. And then when we were able to do this on one of our other machines that allowed Noncoplanar, like you can see there’s two partial sagittal arcs there. We were able to bring these iso dose lines and, and keep the dose very sharp left and right.

Kiran Kumar (05:42):

And so I’m going to go to lymphoma. So I am a lymphoma, paediatrics, and sarcoma specialists. So this is something I know well. And lymphomas affect every part of the body. So we have NK T cell lymphomas, which I will always do Noncoplanar for the same reason as that example you just saw. But there is also a lot of times in lymphomas in the mediastinum. And so Matt talked about this a little bit, but this is extremely important.

Kiran Kumar (06:07):

So anyone who treats lymphoma knows that these patients are often young and they have excellent outcomes, right? The large majority are living long term. But the big problem with radiation and why, you know, so many of our medical oncology colleagues are trying to get rid of us is because they’re worried about these long-term effects. And specifically they’re worried about heart and they’re worried about secondary lin. See breast cancer. And so here’s a nice study that compared both coplanar, Noncoplanar, VMAT and coplanar IMRT with a variable number of beams and Noncoplanar IMRT with variable number of beams. And you can see here, you know, for both of these, the solid blue line is the Noncoplanar arc, which had significantly reduced heart dose and breast V four. So just with the breast, for those of you who don’t know, just any amount of breast tissue getting four gray or more has an increased risk of secondary malignancy. And so if you’re treating to 30 Gy or whatever we normally do for lymphoma, keeping the 4 Gy iso-dose line off the breast can be very, very challenging, right? And this graph shows how the more beams helps, especially if they’re Noncoplanar beams. And then obviously the Noncoplanar arc can make a big difference.

Kiran Kumar (07:16):

And I think seeing images for me is always better than looking at charts and numbers. And so here, you know, most people would probably treat this with VMAT, right? And so VMAT is the second box, but with VMAT you’re spreading dose kind of left, right? Right. The lungs, the breast, what I’m most concerned about there is the breast, right? If you look at the butterfly VMAT or the Noncoplanar with 15, you know, different angles of the IMRT that’s significantly sharper, keeping this dose anterior-posterior much better. And that is a huge difference in terms of long-term secondary malignancy risk.

Kiran Kumar (07:56):

Okay, so switching gears out of lymphoma to breast. And so breast cancer is another you know, site where people are trying different beam arrangements to see if you could reduce dose to the contralateral breast. It’s often most concerning in left side of breast cancer. And when you’re treating the IM nodes, so this was a study of 20 patients left-sided treating the IM nodes and they compared non-complaint or VMAT to co-plan or VMAT and 3D plans. And they showed that this non-coplanar VMAT has significantly reduced the dose to the heart and ipsilateral lung compared to coplanar and 3D, and also reduced the dose to contralateral breast and lung compared to coplanar. VMAT ended up being similar to 3D. And these numbers are meaningful, right? There’s a 28% reduction in mean heart dose, a 20% reduction in ipsilateral lung dose, a 53% improvement in the conformity index. So these plans are much more conformal. So this is very powerful, right? When, and a lot of times we’re doing this com comprehensive nodal radiation for these breast cancer patients. And just doing IMRT may not be enough if you’re doing coplanar IMRT. Okay, so the last few cases I want to show, so this is in lung cancer. So I think you know, most people who’ve done lung SBRT or SAB

R are very familiar with using coplanar and non-coplanar treatments. And so these are some studies showing how Noncoplanar partial arcs could significantly reduce the lung V20 which obviously is important for radiation pneumonitis risk, but also the max dose cord esophagus, large bronchus, aorta, and trachea.

Kiran Kumar (09:34):

And a lot of these, you know, especially at UT Southwestern, I’m sure a lot of institutions were coming back and retreat, right? People are getting more lung mets, you have to come back. And so these are very important not just for that plan, but for planning ahead. And the next case I have kind of illustrates this. So this is a 71-year-old who had a non-small cell lung cancer of the right upper lobe, which was treated and then had a recurrence about four years later and had two anterior nodules in the right upper lobe recur in the vicinity to where the primary tumor was. And so in this case, we did SBRT, we did 50 grade and five fractions, but we’re very, very concerned with the dose to all that long and near there as well as going into the major vessels and the heart, the contralateral side.

Kiran Kumar (10:19):

And so you could just see this plan using these Noncoplanar arcs, how tight and conformal these isod dose lines were. And this patient is now two years since the re-treatment. No toxicities from this has been disease free. The last site that I want to talk about is the CNS. So again, Matt talked a little bit about this. And so, you knowing hippocampal avoidance, but just in general, right, with any primary brain tumors using Noncoplanar, either VMAT or using Noncoplanar beams with IMRT can significantly reduce the dose to a lot of these structures we care about hippocampus, temporal lobes, cochlea, contralateral oar. And we had our own in-house study for hippocampal avoidance, whole brain led by a lot of our physicists and we studied coplanar versus Noncoplanar with the vertex arc and found, just like Matt showed in the other study, significant improvement in hippocampal sparing.

Kiran Kumar (11:13):

And you can see some of the numbers here complaining comparing the Noncoplanar to coplanar and its hippocampal, D100, D max, all of these were improved using the vertex arc. The maybe next to last case that I’m showing here. So this is something that’s near and dear to me. So I do lymphoma, and I also do pediatrics. So this is a study that looked at cranio PHNs, which you get in adults or kids. This had 10 patients and you can see from some of these images if you had just done this with either a conformal arc or a conformal VMA plan, trying to treat this cranio phenoma, but sparing the bilateral hippocampus, is very difficult. But these, this is not a malignancy, right? These are benign tumors. These kids are going to live long normal lives, but the radiation dose of the hippocampus is going to be what drives their long-term neurocognitive outcomes, their decreased iq, and decreased performance in school.

Kiran Kumar (12:08):

And so just a simple thing of using a non-coplanar arc in, instead of just doing coplanar reduce the dose to the bilateral hippocampi by 4 Gy. So from 10.8 Gy to 6.5 Gy. And if you look at the pediatric literature, 6 Gy or higher is where you get these long-term effects and every, and it’s not just the threshold, right? Every Gy, it’s kinda like the heart, like 6 Gy is better than 8 Gy, which is better than 12 Gy. Like every dose matters. And so this is pretty meaningful for, for these patients. And here’s another example. This is an older patient who had a malignant meningioma of the right frontal parietal region. And again, when you have especially these lateralized brain to tumor seven for fractionated treatment, this was 60 Gy 30 fractions using these Noncoplanar beams could significantly reduce the dose to the rest of the brain.

Kiran Kumar (12:59):

And so my last slide is on why non why, why not Noncoplanar? Sorry, double negative. And so, you know, many people, if you ask them, these are the common complaints, right? So treatment time is obviously the biggest and you know, and it’s not just the time for the patient by doing a couch kick or whatever, but all the physicists on here know and everyone else knows just the time for planning for dry runs. If something’s non-deliverable, the delays of, you know, replanning and repeat QA, all of these things. So that’s a problem, right? Fortunately, we have solutions the treatment time for the patient. And concern about infra fraction patient motion, concern about the delivery accuracy. And then finally collisions, right? Patient safety collisions. Anytime we’re doing these more complicated plans with a non-coplanar plane, that’s always a worry.

Kiran Kumar (13:53):

But, you know, I think the beauty is now with these novel technologies that we have, it really takes away a lot of these barriers. And so it’s more just, at least on the physician end, on the clinician end, we’re thinking. It’s not for every patient, it’s not for every treatment, but often you don’t realize until you try. And so this is my, I run the residency program, so this is my like, education hat. I always tell my residents, like, if you don’t even ask, no one’s going to do it, because it’s so much more work. Dosimetry is not just going to throw in a Noncoplanar arc if you don’t say anything, but if you bring it up and you actually ask and you say, let’s create two plans, let’s compare these. It may not be different, but it might be pretty significant. And these are things that people just don’t realize but can make a huge difference in patient care.