So, as we all know that radiosurgery for brain metastases has become a very busy practice for our specialty. And brain metastases has become more and important health problem for our patient because the incidence keep increasing. And at least 20% to 40% of cancer patient ultimately will develop brain metastases. And because we have more successful systemic therapy and improvement than other treatments, our patients survival keep increasing. And also, we have much more advanced imaging techniques with advanced high resolution MRI scan, so we're really seeing a different patient population, we're picking up brain metastases much earlier, but we are just seeing a lot of patient with multiple brain metastases. And this will become a challenging task for us how to optimize treating those patient. Because at this point, I think everybody's very clear that for a significant amount of patient with brain metastases, really aggressive treatment is the treatment of choice for them, no longer truly a palliation situation.
So as mentioned, radiosurgery for limited brain metastases is very much standard of care and is based on high level of evidence with multiple publications. And omitting whole brain radiation treatment has been proven not to compromise survival and has been shown to reduce neurocognitive decline. There's much more accumulating data indicating that with more brain metastases radiosurgery alone will be a proper treatment. I just listed some of the key publication with prospective data or large retrospective series. And it's evident that patient with two to four brain metastases favor very similarly to patient with four, five, or more brain metastases if they're treated with radiosurgery alone. So that really increased indication for patient who should be evaluated for radiosurgery upfront, and also now we are dealing with patient with more and more brain metastases need to be treated at the same time and become a technical challenging for us.
So we have very mature solutions for radiosurgery. And this is just an illustration here with Gamma Knife, CyberKnife, Tomo, and also LINAC-based system. And those are being shown to be effectively treating single or few brain metastases target. But now we have more brain metastases, then we really have to evaluate what's optimal treatments. The zero treatment we have before, just one target at a time works really well when we have one brain metastases or two or three metastases as a solution seems to be a very appropriate treatment option. Now we have multiple brain metastases, 5, 10 or more, then the concomitant become more appealing because the efficiency of the treatment.
And so, that's one of the solution is using the automatic planning system to using mono-isocenter technique for multiple brain metastases. As you are familiar, the Brainlab has Elements software looking at mono-isocenter, a concurrent treatment using dynamic arc for brain metastases. And this is automatic brain metastases planning system and using dynamic arcs with mono-isocenter and consistent rapidly to produce a radiosurgery plan efficiently. And because it's a 3D plan, so we do not need to do patient individual QA. So workflow-wise is more efficient compared to a VMAT solution.
So, our center has started using this software package as in 2015. And in 2016, we published our first comparing study. At this point, we only limited patient with limited brain metastases. So the study is only restricted to patient who has limited number of brain metastases, three or four, and we compared that to Gamma Knife. As you can see, in our initial study with patient who has still quite limited number of brain metastases, the software performed quite well. If you look at the key parameters, V12, V6, V4.5, they are very equivalent to Gamma Knife plan. But when you go to a very low-dose spill, the Gamma Knife did show some, you know, advantages. But the main significant finding is, obviously, treatment time. So all the treatment can be done in a 10 to 15 minutes timeframe with mono-isocenter technique. For Gamma Knife, depends on the source strands and the complexity of plan, you can see the time will be substantially longer.
Subsequently, our practice expand to including patient with more brain metastases. So that's no longer limited for brain metastases. Actually, where I practice, you know, I routinely treat patient up to 10 brain metastases with radiosurgery and potentially more. And so, we look at the treatment performance of different radiation treatment planning system for more brain metastases. This is a study we're looking at 16 clinical patient with 4 to 10 brain metastases, and all of them have 120 brain mets total. And we compare a couple of different techniques, particularly including a Gamma Knife plan, a Element...at this point, the Elements has been upgraded to 1.5 version. And we also have a HyperArc plan, and also we have two individual plan from two centers produce a VMAT plan. So we're looking at inter-planner quality differences.
And this is just an illustration of the plan, a snapshot of the isodose graph. As you can see, the high-dose volume is actually conformal. But when low-dose spill, it seems to be a little bit different between different planning system. The Gamma Knife seems to have some advantages. And this is the result we're looking at the actually V12. And you can see that the plan with Gamma Knife, particularly with low dose, moving from V12 to V6 or V3, showing some advantages. And actually in that studies, the HyperArc performed quite well, had a very good conformality as well as dose spill, showing that improved the mean bring dose as well as low-dose spill, the 6 and 3 grades.
One of the interesting thing we actually identify that is actually there's a dose dependent...I mean volume dependence on those parameters. Particularly looking at the gradient index, you can see the difference is particularly large for very tiny lesions. If you look at 0.6 to 0.8 millimeter cc lesion, the variation between different treatment planning system is very large. But when is going high to the bigger lesion, the difference become much smaller. And it's similar to the V12, but the difference is not that striking.
So actually, we're looking into a little bit more on the physics side and try to evaluate the difference when we're evaluating different planning system, particularly for very small targets. And there's quite a few important information we learn from this evaluation. First of all, the Brainlab Elements software is a software used submillimeter grid for segmentation, and most of the other software like on image and also GammaPlan or Eclipse using 1 millimeter grid. So that actually impact the volume segmentation, so illustrate as the graph on top. So if that lesion is more than 50%, it will be captured in both treatment system. But if it's only a quarter, it will be captured in Elements but will not be captured with a 1-millimeter grid system. So that itself has a volume difference.
And also, you can see that the same icon image, the MRI image will be segments slightly differently just because the resolution of this segmentation are different between 1 millimeter or sometimes submillimeter segmentation. So if this is true, then obviously because of difference, then the GI and the CI become less relevant because we're talking about the volume or segmentally differently particularly for very, very small lesion. Obviously, those changes become much less significant when we bring a large lesion. So this is one of the first finding we find. So when we're doing those much evaluation, we always need to read out those parameters in the native system. And if you change the...push to a third-party system, then you...because the segmentation difference, you actually now compare everything exactly the same.
And this is actually the evaluation we look at it because we plan the HyperArc and Eclipse system, and VMAT and Eclipse system, now also GammaPlan and Elements. So if we actually push the dose and volume from one system to another, then inevitably, there is a discrepancy between other planning system to the Elements because it's submillimeter segmentation. So it's actually always be a bigger volume, because the assumption is smaller will be captured by Elements because submillimeter accuracy, but will not be captured with Elements, either Eclipse or Gamma Knife. So it's actually, you know, favor the other treatment planning system. And same as applied to the volume itself.
And this is because the segmentation of the volume is different, so that actually affects the prescription coverage. So if the prescription coverage is read out in Eclipse but pushed to Elements, we realize that because the volume difference, the coverage actually will be slightly decreased. So actually, we're not seeing this same coverage as we see in the Eclipse system just because the segmentation difference. And all those changes actually favor the Eclipse system or the GammaPlan system compared to Elements.
And since then, we have upgraded our Elements system to the 2.0 system. And this is further improving the arc delineation and planning, and also introducing partial arcs in this to try to address some of the converging dose cloud for connected lesions. And this software actually has been shown in our experience perform better than 1.5. We actually did initial dose comparison using the plan with 1.5, the replan was 2.0, showing substantial improvement in the plan quality. And here, which is showing one plan with a patient with 27 brain metastases using this Elements plan, just showing that we can treat a large number of brain metastases concurrently with a very efficient delivery.
So we are looking to compare this new element system with the HyperArc, which has been shown in a previous study, to perform better than the prior version of the Elements. And this time, we actually utilize the clinical cases that have been treated in UAV, that's including 30 patients with multiple brain metastases and we replan all the patients with our 2.0 system. And when we actually import the system, the dose into Elements because the submillimeter segmentation, we actually see the coverage in the HyperArc plan is actually not as high, is actually varying from low 90s to 99%. But we do 2.0 planning, we normalize everything to 99% coverage of the lesion. So it's more stringent and higher quality plan. And other parameters all read out in the native system. And using Eclipse planning, we were using readout all the parameter like V12, V6, V3. And we read out all those parameters in Elements using the Brainlab Elements software. And all those system treatment was playing with TrueBeam STX with HD MLC system.
And this is example of the planning we see. I think I will just very briefly explain. This patient actually has nine brain metastases. I just want you to pay attention to the most left side of the green curve. That is the normal brain dose. As you can see, they're very similar. And with that particular case, the MME 2.0 plan is a solid line, actually performs slightly better than the HyperArc plan. So if you look at the actual parameters for V12, V6, and V3, actually in that case, the Elements plan perform a little bit superior. And the isodose cloud, as you can see, is the low-dose watch, is a little bit bigger on the HyperArc plan, which is, you know, showing the inner square. And the outside, the background, the isodose cloud is 2.0, which is showing a little bit more conformal.
So we compile all the 30 cases and run the statistic. As we can see that actually those plans are very comparable. So we have equivalent cover dose spill for the V12, V3, and mean brain dose in these two systems and actually they performed very, very similarly. Do bear in mind that the coverage is superior with Elements plan was 99% for all lesions, and the Eclipse plan the coverage is slightly lower.
So in summarize, for this comparison study we have performed so far, I think it's...first of all, those treatment planning systems were performed in general clinical appropriate plans. But when we're looking at the true performance of each planning system, particularly when you practice using lots of radiosurgery for lots of small lesion like less than 1cc, it should be very, very careful regarding probably the dosimeter reader system. Minimally, everything needs to be read out in a native system. Try to push a third-party system and are going to introduce in lots of errors and those are the parameters reader from the third-party system are not going to be reliable just because segmentation changes.
And it's also very clear that when we're treating with multiple brain metastases, it's very beneficial to introduce concomitant treatment techniques because the efficiency. And also I've mentioned the incidence of brain metastases keep increasing and we are looking at 200,000 or more cases and we try to absorb those patients. And we really need to come up with a system that's highly efficient and also produce high quality. So currently, based on our initial experience with the 2.0 system, we feel that it's a very efficient planning system, automatic general plan within a few minutes, and the plan quality has been shown in our dosimeter studies is comparable to HyperArc and the GammaPlan, and we can treat all those lesions in a very efficient timeframe, usually less than 20 minutes. And one thing also to keep in mind that because a 3D plan, that's it's really more efficient for physicists to workflow. That we no longer need patient individual QA as required for VMAT or HyperArc-based planning.
So this is how... The dosimetric comparison study is, obviously, you know, ultimate data need to be validated by clinical experience. So I just want to plug in this radiosurgery registry that's in a collaboration between Brainlab and Stereotactic Radiosurgery Society. And this really has been acquiring and collecting multiple large amount of patient data and encouraged to continue input data. So we capture all the patient parameter, treatment parameters, clinical parameters, as well as outcome. And this is just initial snapshot of what we have so far. And this is preliminary data which we show that over 1,000 patient have captured, just historical compared to a NCI database showing that currently under radiosurgery database that patient perform equally well or better. But obviously, those need to follow longer with more outcome data and validated with look into more detail about patient characteristics.
And lastly, I would just want to thank you my collaborators, particularly people from Thomas Jefferson University, you know, from Pennsylvania, Rutgers University, as well as University of Alabama to help with or perform all those comparison studies. Well, I'm trying to be mindful because of time. I will have our speaker come to present and we'll save the question and answer towards the end. So next, I have Dr. Seymour and he will talk about initial clinical experience from Elements multiple brain metastases radiosurgery.
