SRS for BS lesion: what dose?

[SneakyBooger]

single fraction silliness like 12 Gy.

From the article referenced above:

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[xrthopeful]

Stop citing irrelevant nonsense. If you are using throwaway lines from old small papers to justify a dose, you should be referring out or calling trusted high volume colleagues for advice

 

[Pointless]

The point being, there are easier ways to bilk the system than 5 x 5. The eqd2 of that fractionation for ab=2 is 44 and with the previous wbrt dose is around 80 Gy. To brainstem. We have some serious heavy hitters on this message board if i am honestly being chastised for "only" giving 80 gy cumulative dose to brainstem.

Anyway, there are data to support it, I have found it effective and safe, and I stand by it.

 

[Pointless]

And as a related but separate point, this whole "only I have it figured out and all the other rad oncs are dumb and greedy" mentality is a large part of why this ship will sink, if indeed it does. I think we would all benefit from cutting each other a little slack and supporting each other a little more. After all, we can assume that many of the docs in this field are highly qualified given how competitive it was to get in for a very long time. Can we not assume that there is some actual critical thinking going on outside of our own brains?

 

[xrthopeful]

I agree with you in general but:

A) part of being a good physician is having humility to know when a case is difficult. I feel like I do this all the time. I know when to ask for help.

B) people shouldn’t be looking at throwaway references to justify doses like 12/1 that don’t pass the initial first principles gut check smell test.

 

[Pointless]

No I get it, that wasn't necessarily directed at you. I just hate to see a good discussion descend into the typical rad onc shame fest.

And I certainly concur that discretion is the better part of valor for difficult cases. In this case, I don't honestly believe that referring to a big academic center with an old ass gamma knife (likely planned out by a resident) would improve outcomes. It would be a good way to punt the liability, however....

 

[xrthopeful]

well just like an academic physician knows the community and knows who he trusts to refer to and who he doesn't (whether they don't communicate well or they don't show that they give a crap etc), I think we in practice need to know who to refer to and who not to in a big center (some people will pay more attention and care more than others).

this goes for any field in medicine, or any field or area in life really.

 

[Bequerel]

I can't tell but are you insinuating that the recommendation for 5 x 5 is being driven mainly by desire for stereotactic reimbursement? If so, that's more than a little offensive. If I just wanted to bill for SRS, I could give some weak single fraction silliness like 12 Gy.

30 Gy in 10 fractions = 20 Gy in 5 fractions = 8 Gy in 1 fraction. 12 Gy in 1 fractions is a lot less silly (although not entirely un-silly) than 25 Gy in 5 fractions.

 

[SneakyBooger]

Just bringing data to the conversation. I certainly apologize if it displeases some as that is not my intention.

I have been part of an extremely active radio surgery team for 25 years - I've been in the same center for a very long time. I do refer out some. But, not very often anymore. I referred out quite a bit when I was younger and learned a lot from it.

BTW, I have treated a few brainstem mets with 12 Gy and cannot recall a single local recurrence. Go figure - they die from elsewhere failure. I have a hunch brainstem mets, surrounded by dense fibers and different degrees of vascularity, have a bit different radiobiology.

I still think there is value in reviewing the literature, especially when it doesn't necessarily support my own practice preferences. Keep on learning that way.

BTW, as I previously indicated, that excerpt comes from the reference noted above, published in 2016:

https://www.redjournal.org/article/S0360-3016(16)30320-0/fulltext

 

[Pointless]

30 Gy in 10 fractions = 20 Gy in 5 fractions = 8 Gy in 1 fraction. 12 Gy in 1 fractions is a lot less silly (although not entirely un-silly) than 25 Gy in 5 fractions.

There are many practitioners who wouldn't consider brainstem SRS even without the history of previous WBRT, so I think this proverbial pissing match is a little silly. But if it will end this discussion, then I will declare you the winner. May all of your brainstems go unnecrosed.

 

[Mandelin Rain]

So do we have a dose or what? Or do I refer to the local academic center so that guy can read the same exact data and blindly pick a dose based on a hunch and maybe an anecdotal failure/toxicity that they experienced?

I guess if 1300 cGy is good enough for Harvard, it's good enough for me.

 

[Pointless]

I will just point out the last sentence of the conclusion from the IJROBP article quoted above:

Prior whole-brain irradiation increases the risk of severe toxicity in brainstem metastasis patients undergoing SRS.

I'm staying with my cowardly 2500 cGy in 5.

 

[Mandelin Rain]

I will just point out the last sentence of the conclusion from the IJROBP article quoted above:

Prior whole-brain irradiation increases the risk of severe toxicity in brainstem metastasis patients undergoing SRS.

I'm staying with my cowardly 2500 cGy in 5.

Greedy capitalist pig!

 

[scarbrtj]

This thread is pretty funny and 1) I don't see there's huge disagreement but 2) weird how some people get so entrenched grrr. But if you're thinking about 5 fractions for a brainstem, who knows... maybe 4 fx's would be OK? And maybe 6? But I will never ever never ever do 6 fractions for a brainstem. Because: not science. Billing. And that is Kafkaesque. And that's the rad onc's life. I don't think there's anything wrong with 5 x 5. Somebody mentioned BED10 calcs. Probably, in breast cancer, the right tumor calc is somewhere between BED1.1 and BED8.1. 25/5 almost beats 15/1 at BED8.1. 15/1 kills 25/5 for tumor at BED1.1 though. But, 25/5 should always have less late effects than 15/1. So, hey, 25/5 ain't no slouch. I still like my 15/6+20/4 heh heh.

old ass gamma knife

Good one... have to avoid those ass-gamma knives. They sound horrible.

 

[Pointless]

I'll probably take a look at 6 fraction regimens once Medicare has us all socialized... i kid, i kid.

 

[Pointless]

In all seriousness, I think a lot of the insistence on single fraction SRS is due to inertia from the old days. You know, the days where you screwed a big metal frame into the patient's skull? Fractionating in that scenario was tantamount to torture. Nowadays, however, with frameless treatment... is single fraction really better? I can think of a few reasons offhand why it might not be:

1) We know that LQ doesn't really do a good job estimating equivalent doses at large fraction sizes, so we don't really know what we are giving.

2) We are neglecting to account for at least two of the R's (that are no longer tested on boards in favor of TAQMAN)

3) We have randomized (albeit Italian) data showing equivalent efficacy with lower toxicity with fractionation.

In my practice, if I can't give 24 Gy, I go towards a fractionated approach. Because science (kind of).

 

[scarbrtj]

In all seriousness, I think a lot of the insistence on single fraction SRS is due to inertia from the old days. You know, the days where you screwed a big metal frame into the patient's skull? Fractionating in that scenario was tantamount to torture. Nowadays, however, with frameless treatment... is single fraction really better? I can think of a few reasons offhand why it might not be:

1) We know that LQ doesn't really do a good job estimating equivalent doses at large fraction sizes, so we don't really know what we are giving.

2) We are neglecting to account for at least two of the R's (that are no longer tested on boards in favor of TAQMAN)

3) We have randomized (albeit Italian) data showing equivalent efficacy with lower toxicity with fractionation.

In my practice, if I can't give 24 Gy, I go towards a fractionated approach. Because science (kind of).

They (the Brits?) tried a 19 Gy single fraction for prostate, didn't work too great for high risk (high alpha beta?) with less LC... just as LQ model might predict. The LQ non-applicability at larger fraction sizes is more myth/hand-waving than science if only for the mere fact there is no other more predictive and applicable model at high fraction sizes available. And yes high fraction sizes were used in the original cell survival analyses; if the alpha/beta of a cell line is where the "alpha effects" and the "beta effects" are equivalent on the cell survival curve, you really want that killing effect plotted out to the right of the graph as far as possible for mathematical curve fitting reasons if nothing else. And I have said it before, will say it again: I would expect low long-term local control if I gave 20 Gy in a single fraction to a 1cm NSCLC lung nodule in the lung. Why would I expect something different if that "lung nodule" were in the brain? Also I have said this before but will say it again; your sentiments are more or less summed up here... ~25 years ago.

"I think a lot of the insistence on single fraction SRS is due to inertia from the old days." Like in breast boosting in hypofx e.g. (had to)

 

[Pointless]

Also I have said this before but will say it again; your sentiments are more or less summed up here... ~25 years ago.

OK, but that is an old-ass opinion piece (see what I did there?). We now have randomized data that shows superiority of fractionation, so it's no longer a bunch of old dudes sitting in a smoky room arguing about why their personal opinion is best. Same way we don't quote the Emami tables anymore.

 

[scarbrtj]

OK, but that is an old-ass opinion piece (see what I did there?). We now have randomized data that shows superiority of fractionation, so it's no longer a bunch of old dudes sitting in a smoky room arguing about why their personal opinion is best. Same way we don't quote the Emami tables anymore.

An old-ass but a good-ass opinion piece. Callipygian you might say.

 

[SneakyBooger]

I still like my 15/6+20/4 heh heh.

Scar, I always appreciate your thoughts and would very much like to hear what the rationale is for your choice of treatment.

(Somebody had to say it)

 

[evilbooyaa]

30 Gy in 10 fractions = 20 Gy in 5 fractions = 8 Gy in 1 fraction. 12 Gy in 1 fractions is a lot less silly (although not entirely un-silly) than 25 Gy in 5 fractions.

In terms of tumor control:
15Gy in 1 fraction = 25Gy in 5 fractions.
12 Gy in 1 fraction < 20Gy in 5 fractions.

What's more silly now?

You conflating equal tolerance in regards to purely palliative regimens is not really a fair comparison.

 

[scarbrtj]

Scar, I always appreciate your thoughts and would very much like to hear what the rationale is for your choice of treatment.

(Somebody had to say it)

I don't know there's any secret sauce to it. In someone with a brain met and neurological compromise, my first thought honestly is alleviate symptom first and think about 1 or 2 year local control rates later. This lady is walking around with hemifacial paralysis, can't speak, probably food and water drooling out her mouth when she tries to eat. Miserable. In my career experience I have generally gone from WBRT to WBRT+SRS to SRS only and I find a little less alleviation of neuro compromise with SRS alone, not only in rate of success but also in rapidity of success surprisingly. The problem with WBRT of course is all the downsides. So I add in "partial brain" (tumor plus edema plus margin) fractionated, just a little, upfront to almost all my cases nowadays. On the continuum in tx volume from SRS alone to SBRT, there is less in-brain failure; ie, tx volume is inversely correlated with in-brain failure rate (this is the "upside" of WBRT). But again I don't do WBRT. Just "partial brain lite."

Adding in a little fractionated upfront is actually a good "cheat" too. Most say "I don't treat tumor plus edema." At initial presentation, all brain mets themselves are edematous and swollen from that edema. If you do a little fractionated and rescan, you see a lot less edema and the contrast-enhancing tumor can shrink quite a bit. This makes contouring easier and the tx volume smaller. (And in the meantime maybe the patient's right arm that was partially paralyzed is now usable again.) So maybe you see a 2cm brain met at presentation with a lot of surrounding edema. I treat that plus some margin with 15 Gy/6 fx. Immediately rescan; now I have a much more "clear" tumor border and the lesion is 1.4cm in size (and probably has had symptom palliation). Then I do my 18-20Gy SRS. You might say what does 15 Gy do? "It's not nothing." It almost always gives me good tumor shrinkage. Toxicity correlates with volume in SRS; so I am always treating smaller tumors than I might otherwise w/ SRS alone. Theoretically, if the tumor D-zero is a generous 2.5 Gy, it also gives 0.37^6=0.0025 or almost 3 logs of cell kill. Can't hurt in terms of LC, and it should be very low risk in long run.

And finally for this lady I do think 15/6 plus 20/4 is a little more dose, a little more LC probability, than 25/5. Whether it's more than 15/1, I think it could be. I would expect a smaller brainstem target volume after 15/6... that would enthuse me. 15/6 plus 20/4 it will certainly be less late effects than 15/1. And as I mentioned, maybe more likely to give her palliation. I would consider more dose without a prev hx of WBRT.

 

[Bequerel]

In terms of tumor control:
15Gy in 1 fraction = 25Gy in 5 fractions.
12 Gy in 1 fraction < 20Gy in 5 fractions.

What's more silly now?

You conflating equal tolerance in regards to purely palliative regimens is not really a fair comparison.

I think you’re an excellent moderator and most definitely an outstanding resident. I would’ve made the same argument you are making a few years ago when I was in training, too. You will learn what I’m talking about when you are on your own. The equivalent calculations we learn in radbio just don’t hold up with hypofractionation. 15 Gy in 1 fraction will offer longer local control of a small brain met than 25/5. You only know that after treating dozens and dozens of brain mets over your first few years out of training. I thought I knew it all while in training. You will learn infinitely more during your first couple years after residency, unless you do a palliative fellowship, especially when it comes to palliative cases where there are no clear cut randomized trials or national guidelines to follow.

 

[Mandelin Rain]

You see failures with every/any fractionation. Often about the biology and microenvironment of the tumor which is largely out of your control. Not to sound nihilistic at all. More dose should control more tumors. 24/1 > 16/1. 30/5 > 25/5. Boosted hypofractionated breast > unboosted hypofractionated breast. But alas, best laid plans...

We're all doing the best we can with these non-recipe cases. Are we always perfectly managing the therapeutic ratio for each patient? Of course not. But sometimes your gut tells you to push it, other times you may exercise greater discretion. I won't begrudge those braver or meeker than me unless if they are doing something truly stupid.

 

[evilbooyaa]

I think you’re an excellent moderator and most definitely an outstanding resident. I would’ve made the same argument you are making a few years ago when I was in training, too. You will learn what I’m talking about when you are on your own. The equivalent calculations we learn in radbio just don’t hold up with hypofractionation. 15 Gy in 1 fraction will offer longer local control of a small brain met than 25/5. You only know that after treating dozens and dozens of brain mets over your first few years out of training. I thought I knew it all while in training. You will learn infinitely more during your first couple years after residency, unless you do a palliative fellowship, especially when it comes to palliative cases where there are no clear cut randomized trials or national guidelines to follow.

I certainly appreciate the compliment.

I do agree that rad bio doesn't fully line up for single fraction tx in vivo, but feel that until a better model is outlined, it's the best one we have for the time being.

In regards to the bolded, I'd love to see data for that statement. Maybe I just need to be educated. I know places that treat BMs with both gamma knife and non-gamma knife (linac, Cyberknife, etc.) modalities, and seems like a reasonable chart review that a motivated medical student could do.

In regards to the rest of your post - here's the thing though - I (and my institution) never use 15Gy x 1. Like literally, have not treated with it once during all of residency. Don't think I ever will. If something can't get at least 18-20x1 with reasonable dosimetry then I'm fractionating. Maybe it's because we don't have a GK but I just don't see a scenario that I'm going to treat with 15Gy x 1 until data convinces me to change my practice. My threshold is not high - even a retrospective review like Minitti would get me to strongly re-consider. The U of Alabama retrospective saying 5Gy x 5 with no margin is inferior to 6Gy x 5 with no margin has also influenced my (eventual) practice.

 

[xrthopeful]

It makes sense to try different approaches for things larger than 2 cm IMO because the 90-05 dosing doesn’t work that hot past 2 cm (whether in the 18 Gy range or 15 Gy size range). Whether that’s fractionation or dose escalation or using a multiple staged approach Iike Scarbtj suggests is up to you.

Local control of brain metastases by stereotactic radiosurgery in relation to dose to the tumor margin - PubMed

Use of the RTOG 90-05 dosing scheme for brain metastases is associated with a variable local control rate. Tumors larger than 2 cm are less effectively controlled than smaller lesions, which can be safely treated with 24 Gy. Prospective evaluations of the relationship between dose to the tumor...

www.ncbi.nlm.nih.gov

 

[Bequerel]

I certainly appreciate the compliment.

I do agree that rad bio doesn't fully line up for single fraction tx in vivo, but feel that until a better model is outlined, it's the best one we have for the time being.

In regards to the bolded, I'd love to see data for that statement. Maybe I just need to be educated. I know places that treat BMs with both gamma knife and non-gamma knife (linac, Cyberknife, etc.) modalities, and seems like a reasonable chart review that a motivated medical student could do.

In regards to the rest of your post - here's the thing though - I (and my institution) never use 15Gy x 1. Like literally, have not treated with it once during all of residency. Don't think I ever will. If something can't get at least 18-20x1 with reasonable dosimetry then I'm fractionating. Maybe it's because we don't have a GK but I just don't see a scenario that I'm going to treat with 15Gy x 1 until data convinces me to change my practice. My threshold is not high - even a retrospective review like Minitti would get me to strongly re-consider. The U of Alabama retrospective saying 5Gy x 5 with no margin is inferior to 6Gy x 5 with no margin has also influenced my (eventual) practice.

The wheels have fallen off this thread a bit. I’ve never used 15 Gy

I certainly appreciate the compliment.

I do agree that rad bio doesn't fully line up for single fraction tx in vivo, but feel that until a better model is outlined, it's the best one we have for the time being.

In regards to the bolded, I'd love to see data for that statement. Maybe I just need to be educated. I know places that treat BMs with both gamma knife and non-gamma knife (linac, Cyberknife, etc.) modalities, and seems like a reasonable chart review that a motivated medical student could do.

In regards to the rest of your post - here's the thing though - I (and my institution) never use 15Gy x 1. Like literally, have not treated with it once during all of residency. Don't think I ever will. If something can't get at least 18-20x1 with reasonable dosimetry then I'm fractionating. Maybe it's because we don't have a GK but I just don't see a scenario that I'm going to treat with 15Gy x 1 until data convinces me to change my practice. My threshold is not high - even a retrospective review like Minitti would get me to strongly re-consider. The U of Alabama retrospective saying 5Gy x 5 with no margin is inferior to 6Gy x 5 with no margin has also influenced my (eventual) practice.

I’ve only used 15 or 16 Gy in 1 fraction in this particular scenario, small brain stem lesion. I would also use hypofractionate radiosurgery for lesions too large for 18-24 Gy in a single fraction. I was suggesting that 15 Gy x 1 fraction is not equivalent to 5 Gy x 5 fraction. I was also suggesting earlier that 5 Gy x 5 fraction is an overall weak SBRT palliative dose. If I’m going to go out of my way to treat a patient with a good enough prognosis and to warrant an SBRT palliative treatment with immobilization and daily imaging and planning needed for SBRT I’m going to be more aggressive then 5 Gy x 5 fractions. Otherwise you could just slap on quick AP/PA 20 Gy in 5 fraction field with a 110-120% hot spot and you’re not that far off from your SBRT plan.

 

[Pointless]

You see failures with every/any fractionation. Often about the biology and microenvironment of the tumor which is largely out of your control. Not to sound nihilistic at all. More dose should control more tumors. 24/1 > 16/1. 30/5 > 25/5. Boosted hypofractionated breast > unboosted hypofractionated breast. But alas, best laid plans...

We're all doing the best we can with these non-recipe cases. Are we always perfectly managing the therapeutic ratio for each patient? Of course not. But sometimes your gut tells you to push it, other times you may exercise greater discretion. I won't begrudge those braver or meeker than me unless if they are doing something truly stupid.

And I totally agree with all of this. of course I don't use 25 in 5 for your average brain met. as I said, I will go 24 in 1 or fractionate 9 x 3.

We are talking about this specific case, of a previously radiated brainstem, for which I think 25 in 5 is plenty adventurous. I think to ardently advocate for more dose, or to deride a reasonable approach in favor of escalation, is cavalier at the least.

 

[evilbooyaa]

I’ve only used 15 or 16 Gy in 1 fraction in this particular scenario, small brain stem lesion. I would also use hypofractionate radiosurgery for lesions too large for 18-24 Gy in a single fraction. I was suggesting that 15 Gy x 1 fraction is not equivalent to 5 Gy x 5 fraction. I was also suggesting earlier that 5 Gy x 5 fraction is an overall weak SBRT palliative dose. If I’m going to go out of my way to treat a patient with a good enough prognosis and to warrant an SBRT palliative treatment with immobilization and daily imaging and planning needed for SBRT I’m going to be more aggressive then 5 Gy x 5 fractions. Otherwise you could just slap on quick AP/PA 20 Gy in 5 fraction field with a 110-120% hot spot and you’re not that far off from your SBRT plan.

I simply just disagree with you on the bolded. I feel that 5Gy x 5 and 15Gy x 1 likely have equivalent outcomes with lower expected rates of toxicity with the 5 fraction regimen. I'm only speaking of this in the intracranial setting (as I can't think of a scenario I would use 5Gy x 5 outside of the brainstem), most notably this brain stem lesion. Also you lose out on the conformity of stereotactic technique by just doing AP/PA, which is just as important as the prescription dose you pick, so no, I don't think an AP/PA plan to 20 in 5 and SBRT to 25 in 5 are 'not that far off' from one another.

Agree that 5Gy x 5 is a weak palliative dose when compared to 9Gy x 3 or 6Gy x 5 or 18Gy (or higher) x 1.

 

[Pointless]

The wheels have fallen off this thread a bit. I’ve never used 15 Gy


I’ve only used 15 or 16 Gy in 1 fraction in this particular scenario, small brain stem lesion. I would also use hypofractionate radiosurgery for lesions too large for 18-24 Gy in a single fraction. I was suggesting that 15 Gy x 1 fraction is not equivalent to 5 Gy x 5 fraction. I was also suggesting earlier that 5 Gy x 5 fraction is an overall weak SBRT palliative dose. If I’m going to go out of my way to treat a patient with a good enough prognosis and to warrant an SBRT palliative treatment with immobilization and daily imaging and planning needed for SBRT I’m going to be more aggressive then 5 Gy x 5 fractions. Otherwise you could just slap on quick AP/PA 20 Gy in 5 fraction field with a 110-120% hot spot and you’re not that far off from your SBRT plan.

OK so now 25 in 5 is the same as 20 in 5. I honestly don't understand how your brain works. By BED calcs, your 15 in 1 is equivalent to 25 in 5... but in your mind, one is absolutely correct and the other is just wrong.

 

[scarbrtj]

OK so now 25 in 5 is the same as 20 in 5. I honestly don't understand how your brain works. By BED calcs, your 15 in 1 is equivalent to 25 in 5... but in your mind, one is absolutely correct and the other is just wrong.

just to be fair, i'm following his logic... not agreeing with it really... but 20*120%hotspot=24 Gy. He's saying if you're going to be super-fancy with 25/5, we know super-old school with AP/PA 20/5 is safe, easy, weak, whatever. (But 15/1 is over 9000.... idk.)

 

[Pointless]

just to be fair, i'm following his logic... not agreeing with it really... but 20*120%hotspot=24 Gy. He's saying if you're going to be super-fancy with 25/5, we know super-old school with AP/PA 20/5 is safe, easy, whatever. (But 15/1 is over 9000.... idk.)

I think you're being very kind

 

[scarbrtj]

I think you're being very kind

I think we have to be open to the possibility that 15/1 *could* have more LC than 25/5; nothing violates the LQ model, it's just when we have lack of exact numbers to plug in the formula sometimes we see a result and think "welp that violates LQ"... nah, just we didn't know the right number to plug in (or maybe there's "alpha beta heterogeneity" within the tumor!). There will tend to be more LC with 25/5 with increasing alpha/beta. But for things like breast ca, 15/1 could in fact have more LC. However, since extraordinary claims require extraordinary evidence, I don't see strong evidence that 15/1 is more LC than 25/5... and on paper: late effects, brainstem, prev XRT, et cetera et cetera. But Bq *could* be doing better with 15/1 than others doing 25/5 in this particular clinical scenario we are debating. It is not impossible.

 

[Pointless]

I'll concede that there may be more tumor control at the expense of higher necrosis rates with 15 x 1. I will not concede that 20 in 5 ap/pa is anything close to equivalent to 25 in 5.