Protons are blowing Rad Onc's boat out the CMS water

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elementaryschooleconomics said:
While 4.3% of the proton patients developed fistula in this study, in terms of absolute numbers it's still a relatively small number, so I wouldn't be comfortable stating anything confidently based on this data alone.
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TheWallnerus said:
I feel comfortable telling a patient that SpaceOAR or protons are associated with higher rates of fistula.
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This is the paper I was referencing. Granted it's a bit old-ish.

When looking at "grade 3 to 4 bleeding, ulceration, fistula, stricture, and colostomy that developed at least 6 months after diagnosis and required intervention"...

8.9 per 1000 person-years after intensity-modulated radiotherapy
20.1 per 1000 person-years after proton therapy

Late gastrointestinal toxicities following radiation therapy for prostate cancer

Ho6pnwa.png
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TheWallnerus said:
I feel comfortable telling a patient that SpaceOAR or protons are associated with higher rates of fistula. There’s no p value I can give except for that one retrospective analysis that showed higher rates of GI toxicity with protons. But I don’t find the data neutral, or falsifying, otherwise.
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Steve Frank: ‘this is no way to thank the proton lobby!’
 
TheWallnerus said:
This is the paper I was referencing. Granted it's a bit old-ish.

When looking at "grade 3 to 4 bleeding, ulceration, fistula, stricture, and colostomy that developed at least 6 months after diagnosis and required intervention"...

8.9 per 1000 person-years after intensity-modulated radiotherapy
20.1 per 1000 person-years after proton therapy

Late gastrointestinal toxicities following radiation therapy for prostate cancer​

​

Ho6pnwa.png
​

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So...yes, in aggregate, based on this data and the carbon/proton trial data we've been discussing, along with the known physical and radiobiological properties of protons, especially as it pertains to range uncertainty, I am personally of the opinion (with moderate++ conviction) that using protons for prostate cancer with current technology likely has an increased risk of fistula formation compared to photon radiation. Is it significant and/or clinically meaningful? I'm not sure.

Fortunately for me, I don't have protons, and my immediately adjacent regional competitors also don't have protons, so I never have to have this kind of conversation with patients - thus I can "afford" to have such an opinion, I guess, to express on SDN into the digital void.
 
TheWallnerus said:
they are going to send me to re-education camp
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In re-education “camp” they will play baby shark and it is raining tacos child songs all day and not allow you to sleep. At any time SJF and his army of dominatrix can come in and whip you. You will say “Oh NAPT, you are my daddy” and “protons are amazing” many times over if you want to make it out.
 
Radonc90 said:
More people joining the Proton bandwagon...

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The only surprising thing about this is that Moffitt didn't already have protons.

Lord knows Florida needs this desperately. The people are starved for radiation facilities down there. I heard sometimes you can drive up to 6 minutes between linacs! The horror.
 
Miami has two, Tampa didnt want to feel left out

how many does orlando have? only one? very sad stuff.
 
I am so glad our donor fell through. Someone really wanted us to have protons which we just don’t need. We have literally every other toy in the arsenal and before long admin would start leaning on me to put prostate patients on the damn thing to make up for the additional patients identified in the pro forma who did not in fact magically materialize out of thin air when we got a proton unit. In the right situation they have their place but that is not a midsized Midwest program that already has enough machines to treat beyond our standard capacity.
 
ramsesthenice said:
I am so glad our donor fell through. Someone really wanted us to have protons which we just don’t need. We have literally every other toy in the arsenal and before long admin would start leaning on me to put prostate patients on the damn thing to make up for the additional patients identified in the pro forma who did not in fact magically materialize out of thin air when we got a proton unit. In the right situation they have their place but that is not a midsized Midwest program that already has enough machines to treat beyond our standard capacity.
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In America likely 110+% of patients needing radiotherapy get RT. It’s not like in Cambodia where eg about 1% of patients needing RT get RT. There is no vast untapped RT, or proton, market in America. Protons are zero sum. Proformists seem not to understand this.
 
ramsesthenice said:
I am so glad our donor fell through. Someone really wanted us to have protons which we just don’t need. We have literally every other toy in the arsenal and before long admin would start leaning on me to put prostate patients on the damn thing to make up for the additional patients identified in the pro forma who did not in fact magically materialize out of thin air when we got a proton unit. In the right situation they have their place but that is not a midsized Midwest program that already has enough machines to treat beyond our standard capacity.
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I enjoy having protons. I'm one of the heaviest users here. The number of patients who have had protons for routine prostate is very small (zero?). I don't think we've had any trouble keeping the machine full enough.
 
Neuronix said:
I enjoy having protons. I'm one of the heaviest users here. The number of patients who have had protons for routine prostate is very small (zero?). I don't think we've had any trouble keeping the machine full enough.
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I think you enjoy having protons as an option and I would too. If we had them it would be cool for things like esophageal cancers. I am basing my concerns on our experience with the MR linac. I actually really like it and have easily been its heaviest user which makes sense because I treat the disease sites for which it is most useful. Hasn't stopped some of my colleagues from getting the "its not going to use it's self" talk. It would be cool to have anything as an option. Much less cool when you have to start making decisions based on machine utilization.
 
there are many times i wish i had an MR Linac, mainly abdominal sbrt cases when im lookinh at CBCT and seeing how much the bowel moves ffracyion to fraction. its a cool toy to have.
 
Protons imo are an order of magnitude above MRI linacs when we are talking about clinical value vs costs.

The proton books bulls love to throw out the imrt argument when the lack of data is mentioned, but it all comes back to dollars and sense.... Protons >>>>> MRL >> VMAT/imrt when we are talking costs and that's an important part of any discussion
 
Neuronix said:
I enjoy having protons. I'm one of the heaviest users here. The number of patients who have had protons for routine prostate is very small (zero?). I don't think we've had any trouble keeping the machine full enough.
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I can't remember if we've had this conversation before. But in the absence of data, and continuing use of protons, I will assume you feel like the patients are doing better in general w/ protons. I think you treat a lot of CNS. So I imagine you're just seeing better DVHs more so than less side effects and better tumor control? Just picking your brain re: your logic as we all respect your opinion(s).
 
TheWallnerus said:
I can't remember if we've had this conversation before. But in the absence of data, and continuing use of protons, I will assume you feel like the patients are doing better in general w/ protons. I think you treat a lot of CNS. So I imagine you're just seeing better DVHs more so than less side effects and better tumor control? Just picking your brain re: your logic as we all respect your opinion(s).
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The bulk of my proton cases are younger patients with well lateralized, good prognosis tumors. In those cases you get no dose to contralateral or sometimes even ipsilateral hippocampus (especially meningioma). Integral dose to brain is much lower. White matter changes years later are confined to the treatment space. Is there a clear clinical benefit for cognition? It's hard to know. There is a little bit of data but it isn't that strong.

I don't see young children in my practice, but I see teens and 20 somethings with pediatric tumors like medulloblastoma, anaplastic ependymoma, etc or benign tumors in genetic syndromes like NF2 and such. Those get protons as well. Where do you draw the line for who will benefit from protons in cases like that? Is it age 20? Age 30? I'm thinking about cognition and secondary malignancy primarily, but sometimes you can get a nice sparing of some other structures that should reduce acute or long-term toxicity.
 
Neuronix said:
The bulk of my proton cases are younger patients with well lateralized, good prognosis tumors. In those cases you get no dose to contralateral or sometimes even ipsilateral hippocampus (especially meningioma). Integral dose to brain is much lower. White matter changes years later are confined to the treatment space. Is there a clear clinical benefit for cognition? It's hard to know. There is a little bit of data but it isn't that strong.

I don't see young children in my practice, but I see teens and 20 somethings with pediatric tumors like medulloblastoma, anaplastic ependymoma, etc or benign tumors in genetic syndromes like NF2 and such. Those get protons as well. Where do you draw the line for who will benefit from protons in cases like that? Is it age 20? Age 30? I'm thinking about cognition and secondary malignancy primarily, but sometimes you can get a nice sparing of some other structures that should reduce acute or long-term toxicity.
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Sounds like you're using protons appropriately, unlike what i imagine is happening at the majority of proton centers in the country. There simply aren't enough "appropriate" patients to go around to keep those centers financially viable
 
medgator said:
Sounds like you're using protons appropriately, unlike what i imagine is happening at the majority of proton centers in the country. There simply aren't enough "appropriate" patients to go around to keep those centers financially viable
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Agree 100%.

We have a huge neuro volume here so that helps.

I just reviewed the numbers today and fully 1/3 of the patients on our proton system are CNS cases. That's about double any other disease site.

Now what is the other 2/3? A big mix as you might imagine.
 
Neuronix said:
Agree 100%.

We have a huge neuro volume here so that helps.

I just reviewed the numbers today and fully 1/3 of the patients on our proton system are CNS cases. That's about double any other disease site.

Now what is the other 2/3? A big mix as you might imagine.
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How reasonable and data-driven.

Do you even RadOnc bro? Get those prostates cooking!
 
medgator said:
Protons imo are an order of magnitude above MRI linacs when we are talking about clinical value vs costs.

The proton books bulls love to throw out the imrt argument when the lack of data is mentioned, but it all comes back to dollars and sense.... Protons >>>>> MRL >> VMAT/imrt when we are talking costs and that's an important part of any discussion
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Right now yes. But to be fair, if the insurers decided they were actually going to start reimbursing for a new plan with every fraction with an MR linac it would be a different story.
 
ramsesthenice said:
if the insurers decided they were actually going to start reimbursing for a new plan with every fraction with an MR linac it would be a different story.
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A lot of rad onc patients' insurer is Medicare, and they will pay this 100% of the time (you can bill almost nothing else on the day of an IMRT plan though). (This is somewhat similar to many academic places billing Medicare SABR for 5 fx breast, but IMRT for private ins.) But be that as it may, many insurance co's will pay multiple IMRT plans too for MRgRT, just based on what I've been told. And I have seen a top secret proforma I probably wasn't supposed to have seen. Any umbrage people have against the IMRT boogeyman... MRgRT takes that umbrage and says "hold my beer."
 
So, if florida has 10 centers, that’s 1 center for every 2.1 million people. That means, nationally, we may see >150 centers.

Maybe it won’t go that high, but if you don’t have proton training (vast majority of us), you’re at a significant disadvantage. This is something that worries me about the future and getting a job - getting ignored because CV doesn’t mention protons.
 
RealSimulD said:
So, if florida has 10 centers, that’s 1 center for every 2.1 million people. That means, nationally, we may see >150 centers.

Maybe it won’t go that high, but if you don’t have proton training (vast majority of us), you’re at a significant disadvantage. This is something that worries me about the future and getting a job - getting ignored because CV doesn’t mention protons.
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While I think you're correct in that it may cause trouble for some without formal training in protons who are trying to get a job, I also believe very strongly that one does NOT need to have formal training in protons to be able to prescribe/treat with them.

Fractionated RT ---> SBRT/SRS is a much bigger jump and can cause significantly more harm with mistreatment than is the case with protons.
 
RealSimulD said:
So, if florida has 10 centers, that’s 1 center for every 2.1 million people. That means, nationally, we may see >150 centers.

Maybe it won’t go that high, but if you don’t have proton training (vast majority of us), you’re at a significant disadvantage. This is something that worries me about the future and getting a job - getting ignored because CV doesn’t mention protons.
Click to expand...

I don’t think lack of training is anything to be worried about. Many people take proton jobs with no prior experience. It’s easy
 
RealSimulD said:
So, if florida has 10 centers, that’s 1 center for every 2.1 million people. That means, nationally, we may see >150 centers.

Maybe it won’t go that high, but if you don’t have proton training (vast majority of us), you’re at a significant disadvantage. This is something that worries me about the future and getting a job - getting ignored because CV doesn’t mention protons.
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Consider that there may be a point in the distant distant future (after the commericialization of quantum teleportation)... particle accelerators could replace LINACS, much like LINACS replaced Co-60 units. 😵

Humor aside, it is not unreasonable to consider the chance that future technological advances will equalize costs, improve efficiency of treatment, and decrease impact of uncertainties.
 
RealSimulD said:
So, if florida has 10 centers, that’s 1 center for every 2.1 million people. That means, nationally, we may see >150 centers.

Maybe it won’t go that high, but if you don’t have proton training (vast majority of us), you’re at a significant disadvantage. This is something that worries me about the future and getting a job - getting ignored because CV doesn’t mention protons.
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The proton lobby is our saviour on APM. Similarly, they may be here to help on the job market. Not proton training? No job! I might be down with that and would be willing to train in what is needed. Anything that puts more older people out of work is good for the goose/gander. Some of these people have made enough and cannot learn a single new trick
 
Neuronix said:
younger patients with well lateralized, good prognosis tumors. In those cases you get no dose to contralateral or sometimes even ipsilateral hippocampus (especially meningioma)
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Proton usage makes sense to me in these cases. It certainly makes sense with single field treatment of retinoblastoma. It makes sense to me for a lot of pediatric CNS.

The reasons are two fold. First, the obvious factor that protons stop, integral dose is lower and low dose bath does do bad things in terms of growth, cognition and 2nd malignancies in young people.

The second reason is because these cases do not radically expose the shortcoming of proton therapy, which is a low level of confidence of high dose gradient areas of the plan and uncertainty in absolute dosimetry in areas where you are close to threshold for very high increases in toxicity.

Most CNS disease has shown very little benefit to dose escalation above 54-60 Gy. Dose escalation studies with standard fractionation showed very little benefit but reasonable tolerability.

If you have a 130% hotspot in a 24 Gy CSI plan..no biggie. Same for most of these cases (Grey matter, lateral brain lesions).

But...how would handle these two cases?

1. Small, intact CPA meningioma in relatively young person vs. 2. resected, grade II frontal meningioma in a young person.

I'm guessing photons for 1 and protons for 2?

Have you noticed any untoward necrosis risk?

Finally, someone is going to have to really explain to me what IMPT is. IMPT is not IMRT. IMRT is inverse planning employing nearly infinite degrees of freedom (beam position, MLC program) because dosimetric uncertainty is quite low. (This means the compounding uncertainties of complex plans remain within that 5% window or so where we are comfortable.) IMPT as far as I can tell just means you finding ways to modulate pencil beam proton dose. (magnets or other).

Exploring the advantages of intensity-modulated proton therapy: experimental validation of biological effects using two different beam intensity-modulation patterns - PMC

In current treatment plans of intensity-modulated proton therapy, high-energy beams are usually assigned larger weights than low-energy beams. Using this form of beam delivery strategy cannot effectively use the biological advantages of low-energy ...
www.ncbi.nlm.nih.gov www.ncbi.nlm.nih.gov

I cannot emphasize this paper enough. It was published in 2020 by presumably one of the best proton groups around. What they basically tried to do is establish a robust format for doing cell survival work with protons not photons employing 96 well plates. To get a sense of how robust our cell radiatiors are for photons, people have tried comparing 96 well plates to test tubes and gotten very good correlation.

From the paper:

One of the long-term goals of the whole proton therapy research community is to apply accurate biological dose optimized IMPT plans in clinic. However, the large discrepancy between RBE model predications and experimental data has impeded such progress29. The experimental data from the present study have shown the enhanced biological effects using the two opposed downslope dose fields with increased LETd distribution in the target. However, using LETd as a quantitative input parameter of a phenomenological RBE model, such as the McNamara model, cannot accurately predict the experimental results as shown in the present study and previous studies18,25. The reason for this discrepancy is not completely understood, but it may be caused by the “averaged” nature of the physical quantity LETd which completely neglects the spectral distribution of energy deposition events28. Understanding the underlying reasons why there are large discrepancies between experimental data and model predictions is an ongoing work within the field.
 
communitydoc13 said:
If you have a 130% hotspot in a 24 Gy CSI plan..no biggie. Same for most of these cases (Grey matter, lateral brain lesions).
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The benefit to proton in CSI is to spare all the organs anterior to the spinal canal. Benefit in fatigue, marrow toxicity, nausea, dysphagia, secondary malignancy, etc.

communitydoc13 said:
But...how would handle these two cases?

1. Small, intact CPA meningioma in relatively young person vs. 2. resected, grade II frontal meningioma in a young person.

I'm guessing photons for 1 and protons for 2?

Have you noticed any untoward necrosis risk?
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1. Surgery. If unresectable probably SRS but depends on the details of the case.
2. I would try to enroll on NRG BN003, but if I'm treating I'd probably use proton.

I have not.

communitydoc13 said:
Finally, someone is going to have to really explain to me what IMPT is. IMPT is not IMRT. IMRT is inverse planning employing nearly infinite degrees of freedom (beam position, MLC program) because dosimetric uncertainty is quite low. (This means the compounding uncertainties of complex plans remain within that 5% window or so where we are comfortable. IMPT as far as I can tell just means you finding ways to modulate pencil beam proton dose. (magnets or other).
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IMRT does not use beam position as a free variable. VMAT does this (sort of) for the angles that you specify. Sounds like you have a reasonable understanding otherwise (IMPT is spot position, I believe we specify the size of the spots).
 
Neuronix said:
IMRT does not use beam position as a free variable. VMAT does this (sort of) for the angles that you specify. Sounds like you have a reasonable understanding otherwise (IMPT is spot position, I believe we specify the size of the spots).
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Sorry, didn't mean to imply that computer picks beam position as part of the inverse planning process, just that beam position can be whatever you want because the dosimetry is so simple. (compare this to the difficulty in predicting cell survival for 2 variations of opposed lateral protons and I imagine adding a third field may introduce even more uncertainty).

Do you folks discuss this uncertainty in clinic? Does a paper like the one I linked above resonate with clinical radoncs using protons or does it not register?

When you look at plans are you looking at calculated dose or is there an LET number that you can review? This paper clearly demonstrates how LET is what largely matters (although the authors also explicitly state that their definition of LET is quite limited).
 
communitydoc13 said:
Do you folks discuss this uncertainty in clinic? Does a paper like the one I linked above resonate with clinical radoncs using protons or does it not register?
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I'm aware of the controversies. It doesn't change what we do.

communitydoc13 said:
When you look at plans are you looking at calculated dose or is there an LET number that you can review? This paper clearly demonstrates how LET is what largely matters (although the authors also explicitly state that their definition of LET is quite limited).
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Calculated dose. We don't let multiple beams stop on critical structures like brainstem or optics due to fear about LET/RBE.
 
Neuronix said:
It doesn't change what we do.
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Sounds like you are doing the right things. I'm still going to recommend protons for a miniscule number of my patients. It is not on my list of to haves.

FWIW, I did offer both observation (mutual decision making) and referral for protons to the closest thing I get to one of your patients (early 20's atypical meningioma). She preferred local treatment.

Ironically, the one indication for protons where I used to think "this is crazy" but now makes more sense to me is lymphoma in young people. The prescribed dose is low enough and the volumes poorly defined enough that uncertainties in edge of target dosing probably make very little clinical difference and there is still time for some benefit from reduced integral dose.
 
communitydoc13 said:
Finally, someone is going to have to really explain to me what IMPT is. IMPT is not IMRT. IMRT is inverse planning employing nearly infinite degrees of freedom (beam position, MLC program) because dosimetric uncertainty is quite low
Click to expand...

As others have mentioned, IMRT does not quite have infinite degrees of freedom. You can control 2D fluence and beam angle (with some nuances separating SW vs VMAT)… however you have zero control of dose along the axis of the beam path. Each DOF (angle and fluence) can vary in a near-continuous way (which is where I think your notion of near-infinite comes from) but you X-Rays just keep going regardless of what you are trying to hit. IMPT affords you an additional DOF that it lets you control depth. What may also be true is that IMPT may have yet ANOTHER DOF in LETd.
 
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