Head and Neck Replanning - When to just keep going

[RadOncMegatron]

I was just curious when you guys just push through with a head and neck plan and not re-sim for a replan.

If the patient has loses weight around week 4 then definitely worth it, but at week 6 where a replan will give a only 5 fractions I just say forget it.

I'd like to give at least around 10 fractions of a new plan, otherwise just use the original plan, but was wondering what everyone else does.

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[RickyScott]

I was just curious when you guys just push through with a head and neck plan and not re-sim for a replan.

If the patient has loses weight around week 4 then definitely worth it, but at week 6 where a replan will give a only 5 fractions I just say forget it.

I'd like to give at least around 10 fractions of a new plan, otherwise just use the original plan, but was wondering what everyone else does.

If I am replanning, I usually resim around 34 Gy, mostly due to tumor shrinkage not weight loss. Cant think of a replan done purely for weight loss. Agree with you about 10 fractions.

 

[TheWallnerus]

I was just curious when you guys just push through with a head and neck plan and not re-sim for a replan.

If the patient has loses weight around week 4 then definitely worth it, but at week 6 where a replan will give a only 5 fractions I just say forget it.

I'd like to give at least around 10 fractions of a new plan, otherwise just use the original plan, but was wondering what everyone else does.

So that I no longer have to think about it, I resim and replan every head & neck because essentially they all need a "boost" of some sort (except of course Stage I glottic but that's different), so this work (and one can also call it a cone-down too) is saved for the boost. I do this at fraction 20.

 

[medgator]

I was just curious when you guys just push through with a head and neck plan and not re-sim for a replan.

If the patient has loses weight around week 4 then definitely worth it, but at week 6 where a replan will give a only 5 fractions I just say forget it.

I'd like to give at least around 10 fractions of a new plan, otherwise just use the original plan, but was wondering what everyone else does.

Only exception would be if i don't trust the aquaplast h&n mask anymore because of too much pt mobility secondary to all that weight loss. Therapists are pretty good about notifying me of that during daily setup

 

[Gfunk6]

My RTTs are quite engaged and let me know when the H&N thermoplastic mask starts to get wobbly or destabilized. That is generally the green light to re-plan for me.

Technically, we have a module in MIM where we can superimpose the latest CBCT over the originally planning CT with dose clouds and that can give you a ballpark estimate.

However, I think that TheWallernus' strategy of automatically re-simulating is probably the most reliable.

 

[RadOncMegatron]

So that I no longer have to think about it, I resim and replan every head & neck because essentially they all need a "boost" of some sort (except of course Stage I glottic but that's different), so this work (and one can also call it a cone-down too) is saved for the boost. I do this at fraction 20.

I never trained with BV only with SIB. The more I practice, however, I do like BVs since we automatically get a "replan."

 

[TheWallnerus]

I never trained with BV only with SIB. The more I practice, however, I do like BVs since we automatically get a "replan."

I have stated before but I will restate

/soapbox
1) With SIB, the entire head/neck apparatus is bathed in dose for ~7 weeks. This elongates the toxicity AUC. By doing this just for ~5 weeks and then treating a much smaller volume for ~1.5-2 weeks, the patients will be reporting lessening side effects before the last day of RT.
2) There is literature to support a rescan/replan as a "class solution" in HNSCC
3) Even with concerns about "Can you really sum doses between slightly or majorly differing CT scans," one has to think: the dose is being summed IRL whether you know of it or not in silico. I'd rather know IRL. Confidence is there in dose summing based on thinking how you plan. For example, for the first 50 Gy/25 fx plan, I keep the cord plus margin (always 6mm) max pixel dose at 35 Gy. In some ways I don't even have to have a summed dose plan because I know on the second plan I can keep cord+margin at 10 Gy max pixel dose. (This always reminds me of integrating by parts from calculus.)
4) I use accelerated fraction for the boost/smaller volume most times, e.g. 50/25 for initial, and 14 fractions bid of 1.5 Gy to 21 Gy for the boost, for 71 Gy/39 fractions over ~6.25 weeks. One will realize that this is not very different from the MDACC concomitant boost fractionation (72 Gy/42fx/6wks) which has been proven "better" in some studies. AFAIK SIB fractionation doesn't have as good a demonstrated superior track record as the other known HNSCC altered fractionation regimens. A smaller tx volume "hyperfractionation," and only doing the hyperfx for 7 days total, makes this doable in the community with concurrent chemo.

 

[Ray D. Ayshun]

I have stated before but I will restate

/soapbox
1) With SIB, the entire head/neck apparatus is bathed in dose for ~7 weeks. This elongates the toxicity AUC. By doing this just for ~5 weeks and then treating a much smaller volume for ~1.5-2 weeks, the patients will be reporting lessening side effects before the last day of RT.
2) There is literature to support a rescan/replan as a "class solution" in HNSCC
3) Even with concerns about "Can you really sum doses between slightly or majorly differing CT scans," one has to think: the dose is being summed IRL whether you know of it or not in silico. I'd rather know IRL. Confidence is there in dose summing based on thinking how you plan. For example, for the first 50 Gy/25 fx plan, I keep the cord plus margin (always 6mm) max pixel dose at 35 Gy. In some ways I don't even have to have a summed dose plan because I know on the second plan I can keep cord+margin at 10 Gy max pixel dose. (This always reminds me of integrating by parts from calculus.)
4) I use accelerated fraction for the boost/smaller volume most times, e.g. 50/25 for initial, and 14 fractions bid of 1.5 Gy to 21 Gy for the boost, for 71 Gy/39 fractions over ~6.25 weeks. One will realize that this is not very different from the MDACC concomitant boost fractionation (72 Gy/42fx/6wks) which has been proven "better" in some studies. AFAIK SIB fractionation doesn't have as good a demonstrated superior track record as the other known HNSCC altered fractionation regimens. A smaller tx volume "hyperfractionation," and only doing the hyperfx for 7 days total, makes this doable in the community with concurrent chemo.

Yes. We had some dosimetrist in here in the past few months talking about how archaic sequential boosts are. I think sibs in intact, bulky hn cancer are bad for all the above reasons. I do sib for pretty much all my postops.

 

[RadOncMegatron]

I have stated before but I will restate

/soapbox
1) With SIB, the entire head/neck apparatus is bathed in dose for ~7 weeks. This elongates the toxicity AUC. By doing this just for ~5 weeks and then treating a much smaller volume for ~1.5-2 weeks, the patients will be reporting lessening side effects before the last day of RT.
2) There is literature to support a rescan/replan as a "class solution" in HNSCC
3) Even with concerns about "Can you really sum doses between slightly or majorly differing CT scans," one has to think: the dose is being summed IRL whether you know of it or not in silico. I'd rather know IRL. Confidence is there in dose summing based on thinking how you plan. For example, for the first 50 Gy/25 fx plan, I keep the cord plus margin (always 6mm) max pixel dose at 35 Gy. In some ways I don't even have to have a summed dose plan because I know on the second plan I can keep cord+margin at 10 Gy max pixel dose. (This always reminds me of integrating by parts from calculus.)
4) I use accelerated fraction for the boost/smaller volume most times, e.g. 50/25 for initial, and 14 fractions bid of 1.5 Gy to 21 Gy for the boost, for 71 Gy/39 fractions over ~6.25 weeks. One will realize that this is not very different from the MDACC concomitant boost fractionation (72 Gy/42fx/6wks) which has been proven "better" in some studies. AFAIK SIB fractionation doesn't have as good a demonstrated superior track record as the other known HNSCC altered fractionation regimens. A smaller tx volume "hyperfractionation," and only doing the hyperfx for 7 days total, makes this doable in the community with concurrent chemo.

I agree with #1. Totally anecdotal, but it just makes sense and yes, my memory may be cherry picking, but I think there is less toxicity to the skin mostly since you are treating only 5 vs 7 weeks.

I'm pointing this out b/c it was something just in my head and it's nice to see someone else say it out loud.

 

[evilbooyaa]

I think the 10 fraction-ish minimum for a re-plan makes sense unless it's really dramatic weight loss/tumor shrinkage.

I do sequential boost when I'm doing 50 and 70 only volumes (HPV+ OPhx). I do dose painting plan when I'm doing 3 dose levels (HPV- H&N).

 

[RickyScott]

Yes. We had some dosimetrist in here in the past few months talking about how archaic sequential boosts are. I think sibs in intact, bulky hn cancer are bad for all the above reasons. I do sib for pretty much all my postops.

Seq

I think the 10 fraction-ish minimum for a re-plan makes sense unless it's really dramatic weight loss/tumor shrinkage.

I do sequential boost when I'm doing 50 and 70 only volumes (HPV+ OPhx). I do dose painting plan when I'm doing 3 dose levels (HPV- H&N).

sequential boosts if resim. Otherwise, sib is dosimetrically advantageous.

 

[jondunn]

I think the 10 fraction-ish minimum for a re-plan makes sense unless it's really dramatic weight loss/tumor shrinkage.

I do sequential boost when I'm doing 50 and 70 only volumes (HPV+ OPhx). I do dose painting plan when I'm doing 3 dose levels (HPV- H&N).

why don't you just do two dose levels for all? i don't get why some people choose to do 3.

 

[evilbooyaa]

why don't you just do two dose levels for all? i don't get why some people choose to do 3.

Because RTOG 1016 suggested 2 dose levels was reasonable in HPV+ OPhx with very good outcomes overall.

It's not 'wrong' to do 2 dose levels I suppose for all H&N, but I'm just not at that point yet. I mean historically we did 50, 60, 70 in all H&N, so what's the evidence for it? Is there any published prospective definitive HPV- trial that allowed just 2 dose levels?

That being said, all of H&N is step-wise improvements to reduce toxicity, some of which I do partake in, so even some retrospective data to suggest outcomes are similar... and I'd be open to evolving my practice.

 

[medgator]

why don't you just do two dose levels for all? i don't get why some people choose to do 3.

Gtv, high risk and low risk ctv? Makes sense to me in situations where one side of the neck is chock full of nodes and p16- compared to the other side

 

[jondunn]

Because RTOG 1016 suggested 2 dose levels was reasonable in HPV+ OPhx with very good outcomes overall.

It's not 'wrong' to do 2 dose levels I suppose for all H&N, but I'm just not at that point yet. I mean historically we did 50, 60, 70 in all H&N, so what's the evidence for it? Is there any published prospective definitive HPV- trial that allowed just 2 dose levels?

That being said, all of H&N is step-wise improvements to reduce toxicity, some of which I do partake in, so even some retrospective data to suggest outcomes are similar... and I'd be open to evolving my practice.

HN004 allows two dose levels.

 

[evilbooyaa]

HN004 allows two dose levels.

Well I can no longer get protocols anymore for whatever reason, so if you got it, please PM me!

 

[jondunn]

sent

 

[mheat3]

sent

Can I get one of them copies?

 

[communitydoc13]

SIB for most cases here. Almost never resim for weight loss, may resim for massive early tumor response. Agree ten fractions a reasonable cut point.

RA plans are remarkably robust. Have re-calced many more than have replanned and am usually impressed how they hold up with changes in anatomy.

I use accelerated fraction for the boost/smaller volume most times, e.g. 50/25 for initial, and 14 fractions bid of 1.5 Gy to 21 Gy for the boost, for 71 Gy/39 fractions over ~6.25 weeks. One will realize that this is not very different from the MDACC concomitant boost fractionation (72 Gy/42fx/6wks) which has been proven "better" in some studies.

You are going to have to show me the data where accelerated fractionation really beneficial in setting of chemo. Old MDACC data in XRT alone setting. Accelerated, hyperfractionation very cool for both kinetic and a/b reasons but to my knowledge seems to have largely reached obsolescence in the setting of concurrent therapy.

SIB does provide intrinsic dosimetric advantages due to intention. If you have 2 dose levels, your optimization objectives are trying to find an optimal solution for both coverage and dosimetric heat for both levels. This is never done with sequential planning and typically your lower dose level is functionally much hotter with sequential plans when you evaluate the plan sum.

I do sib for pretty much all my postops.

I actually do less SIB post-op because I get queasy with low dose per fraction in a dissected neck. (probably just old)

 

[TheWallnerus]

You are going to have to show me the data where accelerated fractionation really beneficial in setting of chemo.

Altered fractionation radiotherapy with or without chemotherapy in the treatment of head and neck cancer: a network meta-analysis

Chemotherapy and radiotherapy in locally advanced head and neck cancer: an individual patient data network meta-analysis

 

[gmsquid]

SIB for most cases here. Almost never resim for weight loss, may resim for massive early tumor response. Agree ten fractions a reasonable cut point.

RA plans are remarkably robust. Have re-calced many more than have replanned and am usually impressed how they hold up with changes in anatomy.



You are going to have to show me the data where accelerated fractionation really beneficial in setting of chemo. Old MDACC data in XRT alone setting. Accelerated, hyperfractionation very cool for both kinetic and a/b reasons but to my knowledge seems to have largely reached obsolescence in the setting of concurrent therapy.

SIB does provide intrinsic dosimetric advantages due to intention. If you have 2 dose levels, your optimization objectives are trying to find an optimal solution for both coverage and dosimetric heat for both levels. This is never done with sequential planning and typically your lower dose level is functionally much hotter with sequential plans when you evaluate the plan sum.



I actually do less SIB post-op because I get queasy with low dose per fraction in a dissected neck. (probably just old)

The Dosimetry is far better with SIB. It’s all I do. Better OAR sparing, lower heat, higher conformality. I think acute toxicity is better due to better OAR sparing as well. But at worst, it’s an acute for late toxicity trade.

 

[RickyScott]

The Dosimetry is far better with SIB. It’s all I do. Better OAR sparing, lower heat, higher conformality. I think acute toxicity is better due to better OAR sparing as well. But at worst, it’s an acute for late toxicity trade.

In early days of imrt, there were papers supporting better dosimetry w/sib vs sequential on the original dataset, but that is assuming no resimulation. I have treated 2 colleagues over the course of my career. I resimmed them both.

 

[temujim]

The Dosimetry is far better with SIB. It’s all I do. Better OAR sparing, lower heat, higher conformality. I think acute toxicity is better due to better OAR sparing as well. But at worst, it’s an acute for late toxicity trade.

Just depends on the distance of OAR of interest to high dose PTV in particular. You'll get better sparing with a sequential plan with a lower dose elective (think 40-45 vs 56) if the OAR is 1 cm plus away.

Plus doing an adaptive boost plan is so much easier without recontouring the elective LN volume. Cuts down on the OARs that are needed.

Used to do both sequential and SIB; but have moved mostly to sequential lately. As others have said, resim around 36-40 Gy, and give the final 10-12 fractions with adaptive boost plan.

 

[TheWallnerus]

SIB does provide intrinsic dosimetric advantages due to intention. If you have 2 dose levels, your optimization objectives are trying to find an optimal solution for both coverage and dosimetric heat for both levels. This is never done with sequential planning and typically your lower dose level is functionally much hotter with sequential plans when you evaluate the plan sum.

The Dosimetry is far better with SIB. It’s all I do. Better OAR sparing, lower heat, higher conformality. I think acute toxicity is better due to better OAR sparing as well. But at worst, it’s an acute for late toxicity trade.

I was born and raised on SIB. (SIB was the only option in the early days of IMRT; dose summing was impossible.) I have done SIB, and sequential, as much as anyone (maybe). I am also a bit of weirdo: I do ~100% of my H&N planning (soup to nuts). I was also born and raised to do dosimetry work. What was that tweet with the #womenWhoCurie... in the basement... and that re: the basement "this is our operating room"? It's in the planning & optimization, and looking at old and new scans, that you "operate." The contouring (and writing dose constraints down) is not operating. Having been a (pretty good?) contourer AND planner, and then seeing the real-world outcomes, real-time, as a clinician, and having seen many things both on computer screens and in real humans, I had to leave SIB behind.

TL;DR: respectfully disagree w/ you guys

 

[communitydoc13]

I am also a bit of weirdo: I do ~100% of my H&N planning (soup to nuts).

Wallnerus weird as sh... Must be seeing 3 pts a week!

Gotta send my family to him when they get sick. I'll let them know, "this is the most custom care you will ever get".

...unless of course I want them to get RNI for breast.

 

[TheWallnerus]

Wallnerus weird as sh... Must be seeing 3 pts a week!

I am in the lower 50%ile for busy-ness nationally. It's fine.

But residents who rotate with me, I teach them there are kind of two ways to do things. You can contour, and make some dose constraints, and send those off to the black box of dosimetry. And then dosimetry *waves hands* and *it's magic* you now have a plan to look at. Usually it's accompanied by a verbal "This was the best we could do." And then you squint and grimace and send it back so they can lick the calf over again, sometimes. And then you get new, improved, this-is-really-the-best-we-can-do Plan Deux. And it's maybe the next day or 48h later at this point.

Whereas, you could set down and iteratively see the trade-offs yourself, and plan it yourself ("ultimately the decision is mine"), and have everything done a lot quicker, and more confidently... when the need arises. Often, when beaming high doses of radiation near the brain/eyes/ears/spinal cord, the need arises.

 

[communitydoc13]

But residents who rotate with me

Lucky residents

 

[RickyScott]

Lucky residents

 

[gmsquid]

I am in the lower 50%ile for busy-ness nationally. It's fine.

But residents who rotate with me, I teach them there are kind of two ways to do things. You can contour, and make some dose constraints, and send those off to the black box of dosimetry. And then dosimetry *waves hands* and *it's magic* you now have a plan to look at. Usually it's accompanied by a verbal "This was the best we could do." And then you squint and grimace and send it back so they can lick the calf over again, sometimes. And then you get new, improved, this-is-really-the-best-we-can-do Plan Deux. And it's maybe the next day or 48h later at this point.

Whereas, you could set down and iteratively see the trade-offs yourself, and plan it yourself ("ultimately the decision is mine"), and have everything done a lot quicker, and more confidently... when the need arises. Often, when beaming high doses of radiation near the brain/eyes/ears/spinal cord, the need arises.

I also (frequently at least 50-75% of the time) do my own Dosimetry and primarily only treat HN. What I can achieve with sib is phenomenal. I.e. parotid / oral cavity (including overlap with ptv) means of 18-20 Gy / 20-25 Gy without compromising coverage on many cases. Total constrictor means (including ptvs) under 40-45 with frequency. Also those doses of 18-20 Gy are hyperfractionated more so with sib.

Distance from primary to oar does matter in the diff between sib and sequential, but to get that 2 Gy/fx in again to the boost volume usually means at least 50% of that dose 1 cm away.

Would love to do a planning head to head duel

 

[gmsquid]

In terms of replanning, I evaluate the setup. With vmat the tissue loss usually doesn’t change the plan sufficiently to justify replanning (resim and calc the dose on the new sim). It’s only if the patient cannot fit in the mask to a reproducible setup that I replan

 

[TheWallnerus]

In terms of replanning, I evaluate the setup. With vmat the tissue loss usually doesn’t change the plan sufficiently to justify replanning (resim and calc the dose on the new sim). It’s only if the patient cannot fit in the mask to a reproducible setup that I replan

This is an open question: define "sufficiently." I don't know what "sufficiently" is (or isn't). Herman Suit used to say when hyping protons "There's no clinical indication for even one picogray of dose outside the tumor volume"; there's no clinical indication to have even one voxel's dose IRL not match the TPS. If you Rx 70 Gy and a physicist did some sort of QA that the dose was actually 66.49 Gy, the physicist might pump the brakes. Physicists get anal over greater than even 5% dose discrepancies. A legal mis-treatment in some jurisdictions can be >10% mis-dosing. I bet ~99% of the time >4 weeks into treatment there can be +/-10% dose variations in >1cc volumes in H&N chemoRT without replanning if the sole initial plan is superimposed/re-calc'd on top of the "chrono-distant" CT anatomy (VMAT or not). One can be as anal retentive as one wants, or not, when looking at the dose differences weeks into a H&N treatment. There's always some difference.

(To be clear, there is no right way or wrong way on any of this. Very interesting to discuss.)

 

[temujim]

I also (frequently at least 50-75% of the time) do my own Dosimetry and primarily only treat HN. What I can achieve with sib is phenomenal. I.e. parotid / oral cavity (including overlap with ptv) means of 18-20 Gy / 20-25 Gy without compromising coverage on many cases. Total constrictor means (including ptvs) under 40-45 with frequency. Also those doses of 18-20 Gy are hyperfractionated more so with sib.

Distance from primary to oar does matter in the diff between sib and sequential, but to get that 2 Gy/fx in again to the boost volume usually means at least 50% of that dose 1 cm away.

Would love to do a planning head to head duel

You can do planning duels: https://proknowsystems.com/quality/planning

I trolled the winning lists and would try and hire those dosimetrists. Also make all new potential hires do one of the plans. Don't bother interviewing unless they score 85th percentile plus or something.

 

[RadOncMegatron]

My experience is that overall sequential plans, on the computer, are hotter. If there is only a low volume primary and a node near by, dosimetrically it doesn’t matter much and in my experience, due to skin healing I’ve seen after I reduce my field that’s my preferred route for HPV+.

SIB plans I use for when OARs are a priority or for high volume disease. They are just prettier on the computer.

I do replan for weigh loss / tissue early on as I’ve seen some intense skin reactions, but honestly for these replanning at week four by week 6 they have even more weight loss and the contours pooch out anyway (thankfully rare occurrence). I hesitate to replan just for a primary that has regressed esp. if my OARs were fine in the initial plan. In my experience, the primary anatomy, doesn’t change a whole lot. For nodes I’m more willing as tissue loss is also a factor. I’m more paranoid of underdosing tumor though what everyone else said here is very reasonable.

Is this a conversation people have on the outside regularly?

More importantly- DID @TheWallnerus SAY HE PLANS HIS OWN HEAD AND NECK PLANS?!?!

 

[temujim]

I am in the lower 50%ile for busy-ness nationally. It's fine.

But residents who rotate with me, I teach them there are kind of two ways to do things. You can contour, and make some dose constraints, and send those off to the black box of dosimetry. And then dosimetry *waves hands* and *it's magic* you now have a plan to look at. Usually it's accompanied by a verbal "This was the best we could do." And then you squint and grimace and send it back so they can lick the calf over again, sometimes. And then you get new, improved, this-is-really-the-best-we-can-do Plan Deux. And it's maybe the next day or 48h later at this point.

Whereas, you could set down and iteratively see the trade-offs yourself, and plan it yourself ("ultimately the decision is mine"), and have everything done a lot quicker, and more confidently... when the need arises. Often, when beaming high doses of radiation near the brain/eyes/ears/spinal cord, the need arises.

A wall(ne)rus after my own heart. I do all my own 3D planning (just so much faster) and the occasional IMRT plan. Then invite the dosimetrists to beat it. Educational all around.

 

[gmsquid]

This is an open question: define "sufficiently." I don't know what "sufficiently" is (or isn't). Herman Suit used to say when hyping protons "There's no clinical indication for even one picogray of dose outside the tumor volume"; there's no clinical indication to have even one voxel's dose IRL not match the TPS. If you Rx 70 Gy and a physicist did some sort of QA that the dose was actually 66.49 Gy, the physicist might pump the brakes. Physicists get anal over greater than even 5% dose discrepancies. A legal mis-treatment in some jurisdictions can be >10% mis-dosing. I bet ~99% of the time >4 weeks into treatment there can be +/-10% dose variations in >1cc volumes in H&N chemoRT without replanning (VMAT or not). One can be as anal retentive as one wants, or not, when looking at the dose differences weeks into a H&N treatment. There's always some difference.

(To be clear, there is no right way or wrong way on any of this. Very interesting to discuss.)

That’s true, but the goal of 95% coverage to the PTV is that 95% of the time each point in the CTV is getting rx. No setup is perfect and one of the inherent things we do with fractionation is feather dose.

 

[temujim]

My experience is that overall sequential plans, on the computer, are hotter. If there is only a low volume primary and a node near by, dosimetrically it doesn’t matter much and in my experience, due to skin healing I’ve seen after I reduce my field that’s my preferred route for HPV+.

SIB plans I use for when OARs are a priority or for high volume disease. They are just prettier on the computer.

I do replan for weigh loss / tissue early on as I’ve seen some intense skin reactions, but honestly for these replanning at week four by week 6 they have even more weight loss and the contours pooch out anyway (thankfully rare occurrence). I hesitate to replan just for a primary that has regressed esp. if my OARs were fine in the initial plan. In my experience, the primary anatomy, doesn’t change a whole lot. For nodes I’m more willing as tissue loss is also a factor. I’m more paranoid of underdosing tumor though what everyone else said here is very reasonable.

Is this a conversation people have on the outside regularly?

More importantly- DID @TheWallnerus SAY HE PLANS HIS OWN HEAD AND NECK PLANS?!?!

When you move to monte carlo planning, you'll find the sequential plans are LESS hot.

So glad I'm not the only one doing my own HN plans. Previously only knew one other guy IRL doing that.

 

[TheWallnerus]

When you move to monte carlo planning, you'll find the sequential plans are LESS hot.

Marked "true"

 

[TheWallnerus]

That’s true, but the goal of 95% coverage to the PTV is that 95% of the time each point in the CTV is getting rx.

Two things...

First, the "95% coverage to the PTV" thing is purely a dosimetric normalization and is exactly the same as "picking a Rx isodose line" to prescribe to from the "old days." The way that we get "95% of the time" coverage to the CTV is by adding a (properly selected and optimal) setup error margin to the CTV... also known as the PTV. It's a nuanced point.

Second, we are not only concerned with CTV and PTV doses in re-plans.

 

[communitydoc13]

When you move to monte carlo planning, you'll find the sequential plans are LESS hot.

I don't know.

Validation of the Acuros XB dose calculation algorithm versus Monte Carlo for clinical treatment plans - PubMed

Overall, an outstanding agreement was found between the Boltzmann equation solver and Monte Carlo. High-accuracy dose computation algorithms have matured to a level that their differences are below common experimental detection thresholds for clinical treatment plans. Aside from residual...

pubmed.ncbi.nlm.nih.gov

Impressed that both you and Wallnerus do your own plans. Should be commended.

But IMO, we can get carried away with the confidence in our dosimetry. Classic example is taking the same SBRT lung plan run through a AAA vs Acuros dose engine. Plans will look way different but probably not clinically significant.

Likewise, the Mobius QA check. Can be a +/- 5% proposition depending on target size and tissue heterogeneity.

In H&N, we are largely treating mucosal lesions at an air interface without bolus. Seems to work.

I believe that our photon dosimetry, which is now better than our photon dose measurement, is still roughly a +/- 5% prospect. My late effects are overwhelming influenced by tumor size, tumor location and tumor infiltration.

Can't imagine the proton dosimetry.

 

[gmsquid]

Marked "true"

That’s debatable. Max point will be higher with Monte Carlo planning in sib plans due to more uncertainty and the feathering effect of sequential plans. Overall volume of heat will be higher in sequential plans as you need the heat to get the coverage and create falloff

 

[temujim]

I don't know.

Validation of the Acuros XB dose calculation algorithm versus Monte Carlo for clinical treatment plans - PubMed

Overall, an outstanding agreement was found between the Boltzmann equation solver and Monte Carlo. High-accuracy dose computation algorithms have matured to a level that their differences are below common experimental detection thresholds for clinical treatment plans. Aside from residual...

pubmed.ncbi.nlm.nih.gov

Impressed that both you and Wallnerus do your own plans. Should be commended.

But IMO, we can get carried away with the confidence in our dosimetry. Classic example is taking the same SBRT lung plan run through a AAA vs Acuros dose engine. Plans will look way different but probably not clinically significant.

Likewise, the Mobius QA check. Can be a +/- 5% proposition depending on target size and tissue heterogeneity.

In H&N, we are largely treating mucosal lesions at an air interface without bolus. Seems to work.

I believe that our photon dosimetry, which is now better than our photon dose measurement, is still roughly a +/- 5% prospect. My late effects are overwhelming influenced by tumor size, tumor location and tumor infiltration.

Can't imagine the proton dosimetry.

Acuros is pretty good; almost as good as MC. It really took a few months for dosimetry and physics to work out the kinks in MC. We recalculated a bunch of plans from CC to MC and it was eye opening. But those patients did well.... so your point of clinical relevance well taken. But would rather see something on the computer screen that is closer to "reality". And as we proceed down a de-escalation path for many HPV patients, this may become more relevant.

We looked at a variety of ways to handle bone/soft tissue and soft tissue/air interfaces. Ended up not really being necessary.

Tightened up passing requirements with MC as well -- think 2%/2mm now.

Totally agree about proton dosimetry. Way too much handwaving. And claims about field matching and robust planning for larger lesions are sketchy imho.

 

[radiation]

Great discussion. I think for intact HN, as we move away from big elective volumes and focus more on gross disease, having " hot" plans may actually be better. A principle in stereotactic planning is the dose falloff is generally better in the 40-80% IDL range. We don't do this for conventional head and neck because our PTVs include a lot of normal tissue and hotspots in CTV and beyond likely suboptimal. But I'm sure most of us wouldn't mind some "hot spots" in the GTV of a T4 or N3 mass with the added benefit of better dose falloff. I also think the way David Palma is doing things make sense to me

Does 5 + 5 Equal Better Radiation Treatment Plans in Head and Neck Cancers?

Accurate contouring in head and neck cancer (HNC) is critical. International consensus guidelines recommend the 5 + 5 mm rule for expansions around the primary tumor, wherein high- and low-dose clinical target volumes (CTV-P1 and CTV-P2, respectively) are created using successive 5 mm expansions...

www.advancesradonc.org

If you give the GTV 70, the natural falloff from that is going to make a secondary dose level that will likely cover microscopic disease, especially for something like HPV+ disease.

 

[temujim]

Great discussion. I think for intact HN, as we move away from big elective volumes and focus more on gross disease, having " hot" plans may actually be better. A principle in stereotactic planning is the dose falloff is generally better in the 40-80% IDL range. We don't do this for conventional head and neck because our PTVs include a lot of normal tissue and hotspots in CTV and beyond likely suboptimal. But I'm sure most of us wouldn't mind some "hot spots" in the GTV of a T4 or N3 mass with the added benefit of better dose falloff. I also think the way David Palma is doing things make sense to me

Does 5 + 5 Equal Better Radiation Treatment Plans in Head and Neck Cancers?

Accurate contouring in head and neck cancer (HNC) is critical. International consensus guidelines recommend the 5 + 5 mm rule for expansions around the primary tumor, wherein high- and low-dose clinical target volumes (CTV-P1 and CTV-P2, respectively) are created using successive 5 mm expansions...

www.advancesradonc.org

If you give the GTV 70, the natural falloff from that is going to make a secondary dose level that will likely cover microscopic disease, especially for something like HPV+ disease.

I don't use an intermediate volume -- but if you rely on fall off to take care of something you feel should be treated; better to define it and make sure. Otherwise apparently 7.4% of the time you'll get fooled.

And always take these planning studies with a grain of salt... skill of the dosimetrist(s) can make a huge difference.

Looked at the figures in the paper.... CTV shouldn't go back into the prevertebral muscles. I would get after a resident who did that... if I had a resident... both the residents and I agree it is better that way.

Big against hot spots in HN -- but don't have data to really back it up, just inferences.

 

[RickyScott]

Great discussion. I think for intact HN, as we move away from big elective volumes and focus more on gross disease, having " hot" plans may actually be better. A principle in stereotactic planning is the dose falloff is generally better in the 40-80% IDL range. We don't do this for conventional head and neck because our PTVs include a lot of normal tissue and hotspots in CTV and beyond likely suboptimal. But I'm sure most of us wouldn't mind some "hot spots" in the GTV of a T4 or N3 mass with the added benefit of better dose falloff. I also think the way David Palma is doing things make sense to me

Does 5 + 5 Equal Better Radiation Treatment Plans in Head and Neck Cancers?

Accurate contouring in head and neck cancer (HNC) is critical. International consensus guidelines recommend the 5 + 5 mm rule for expansions around the primary tumor, wherein high- and low-dose clinical target volumes (CTV-P1 and CTV-P2, respectively) are created using successive 5 mm expansions...

www.advancesradonc.org

If you give the GTV 70, the natural falloff from that is going to make a secondary dose level that will likely cover microscopic disease, especially for something like HPV+ disease.

One part of the head and neck where I am hesitant about hot plans is true larynx/hypopharynx

 

[jondunn]

One part of the head and neck where I am hesitant about hot plans is true larynx/hypopharynx

Agreed. That is the only place where I watch the heat. Can get bad edema

Otherwise I’ll take heat to facilitate super tight Normal tissue sparing any day

 

[evilbooyaa]

I wouldn't feel great about a > 110% in a mucosal primary, but the center 1-2cm of a 6cm LN? sure. Rare scenarios it could be OK.