SRS for BS lesion: what dose?

[Kroll2013]

young female, known to have a metastatic breast cancer, since 5 years.
In 2017, she developed secondary lesions in the brain with positive CSF.
She receives 30Gy/10 fr whole brain radiation, with intra-thecal chemotherapy.

A month ago, she developed gait disturbances with blurred speech an hemifacial paresia.
Brain MRI showed a solitary secondary lesion, 1.5 cm involving the left middle cerebral peduncle with extensive edema. No signs of meningeal disease.
Pet CT : NED outside the brain.

She was referred for brain SRS.

I need your advice concerning the dose and fractionation SRS vs FSRT, noting the close proximity of the BS and the Hx of Brain RT.

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[scarbrtj]

Your guess is as good as ours. I thought about this for a bit; here's my guess: 15 Gy in 6 fractions to tumor plus edema plus a fair half cm or so margin. Then get a new high res MRI and within 5 days of finishing the 6 fractions make and start a new very conformal just-tumor plan of 20 Gy in 4 fractions as a boost. I can explain that further if you want. I did some calcs and made some CNS-forgiveness assumptions
One thing else. She seems to have fibers from the nucleus of CN-VII going through this. At pretty much any dose you think of doing, there's going to be a risk her CN-VII paralysis may never recover. I'd tell her about that, but also that alternatives to non-CN-VII recovery in her case are worse than a tumorigenic Bell's palsy. Her gait disturbances (she prob has dysdiadochokinesis and past pointing too), due to MCP fiber involvement, may also not really recover. Tough to know what risk to quote for either thing.

 

[Pointless]

No right answer but I would lean toward 5 x 5 with 0 margin. If she hadn't had previous WBRT, could push to 6 x 5.

 

[xrthopeful]

Your guess is as good as ours. I thought about this for a bit; here's my guess: 15 Gy in 6 fractions to tumor plus edema plus a fair half cm or so margin. Then get a new high res MRI and within 5 days of finishing the 6 fractions make and start a new very conformal just-tumor plan of 20 Gy in 4 fractions as a boost. I can explain that further if you want. I did some calcs and made some CNS-forgiveness assumptions
One thing else. She seems to have fibers from the nucleus of CN-VII going through this. At pretty much any dose you think of doing, there's going to be a risk her CN-VII paralysis may never recover. I'd tell her about that, but also that alternatives to non-CN-VII recovery in her case are worse than a tumorigenic Bell's palsy. Her gait disturbances (she prob has dysdiadochokinesis and past pointing too), due to MCP fiber involvement, may also not really recover. Tough to know what risk to quote for either thing.

Hmm - so the dose you're suggesting is 35 Gy/10, with potentially a break in there. Doesn't seem much higher than super standard palliative dose of 30/10 which we use all the time to the whole brain, my concern for CN 7 nerve injury with that dose would be low

I also think I would go higher than 35/10. 15 Gy in 1 is commonly done for brainstem lesions. Could fractionate too (3-5 fx), think it makes sense (given prior WBRT)

 

[mavrik13]

Sorry to be a bummer, but my first thought is if you're not sure what to do in this case, would suggest referring onto larger centre with CNS experience. This is a good case for frameless GK allowing you to fractionate with high precision. For what it is worth, fractionate (5fx is reasonable) with no CTV margin and smallest PTV margin you can accommodate. I'd take the dose as high as you're comfortable with - 25/5 is still pretty hot to normal brainstem considering it has had previous 30/10, but likely small volume.

Without prior RT, often do 24/3 if small, or 30/5.

 

[scarbrtj]

Hmm - so the dose you're suggesting is 35 Gy/10, with potentially a break in there. Doesn't seem much higher than super standard palliative dose of 30/10 which we use all the time to the whole brain, my concern for CN 7 nerve injury with that dose would be low

I also think I would go higher than 35/10. 15 Gy in 1 is commonly done for brainstem lesions. Could fractionate too (3-5 fx), think it makes sense (given prior WBRT)

How is 15/1 "higher" than 35/10. And we do not commonly use 30/10 after 30/10.

 

[scarbrtj]

You can prob miss most of the "meat" of the previous irradiated brainstem by smart dosimetry and beam arrangement (I'd go kind of Statue of Liberty--co-planar, just not in the horizontal plane, a cattywumpus plane--here; too bad I can't explain that). My point is the CN fibers (CN VII in light blue, if you can read backwards) are closer to the lesion (red) than the nucleus. I would stay out of brainstem as much as possible with the dose and let it spill to other areas. Since she already has a CN VII toxicity, we know that RT may or may not alleviate that. That's what we really want: tumor toxicity elimination and tumor control. Tumor control, and length of tumor control, would ordinarily be the top priority, but this is a woman with a history of positive CSF fluid, multiple brain mets, and previous CNS RT. The previous RT really blunts how aggressive you can be here, but I think you can forgive a fair amount of the previous dose.

 

[Neuronix]

I need your advice concerning the dose and fractionation SRS vs FSRT, noting the close proximity of the BS and the Hx of Brain RT.

No right answer. I'd do 15 Gy in 1 fraction with no margin on Gammaknife with frame.

 

[medgator]

I think this is one of those scenarios where I would feel comfortable with rigid fixation/frame, single or multi fraction

 

[BobbyHeenan]

No right answer. I'd do 15 Gy in 1 fraction with no margin on Gammaknife with frame.

I've done it this way or 25-30 Gy in 5 frameless on linac. Anecdotally have seen no difference in control or side effects/necrosis with either approach. I tend to fractionate anything > 1 cm in the brainstem, > 2cm elsewhere (9 X3, or 6 X 5).

Really wish we had a randomized trial (obviously prob not enough brainstem patients) for larger mets single vs. multi fraction. Retrospective stuff is helpful, but would love to see something randomized and would definitely enroll. We had success enrolling on the post op SRS vs. WBRT trial (though I think those SRS doses were wayy too high) so I don't see why we couldn't get patients on another trial, but I know there's no funding for a trial like this.

 

[scarbrtj]

Non-random article citations. "Preserve the facial nerve." Or in this case try to heal it. Single SRS-ing in this particular anatomic region (kind of like an acoustic case) more assoc w/CN VII dysfunction than multi-fx. Also, single shot SRS more assoc w/ RN, less assoc w/ LC, than multi-fx. In my own anecdotal experience, more apt to return CNS function lost due to tumor with multi-fx than single shot. And another look at CN VII and location for her, perhaps informing dose planning/beam planning...

Regardless what dose chosen, I don't see a need for single shot. Wouldn't be more BED for most anything but late effects. Single-shotting above 13-14 Gy in this region does have a measurable CN toxicity. (Maybe late toxicity won't be too much of a thing for her sadly.)

 

[Neuronix]

Regardless what dose chosen, I don't see a need for single shot. Wouldn't be more BED for most anything but late effects. Single-shotting above 13-14 Gy in this region does have a measurable CN toxicity. (Maybe late toxicity won't be too much of a thing for her sadly.)

That's why I wrote that there is no right answer. Everything we're writing is based on opinion, anecdote, and retrospective data.

Is it better to fractionate with a margin or single fraction with no margin? Even if you plan to use an Ikon system to fractionate without a margin, the stereotactic accuracy without a frame is not as good as with a frame. Do you still accept no margin in those cases?

Less than 15-16 Gy does not provide enough control IMO. Brainstem toxicity is real, but death is a bigger problem. Some people with single fraction SRS would argue the other way around and just give 12 Gy to minimize any possible treatment related harm.

For further discussion with the largest series of single fraction plus review of the relevant literature, see: Stereotactic Radiosurgery for Brainstem Metastases: An International Cooperative Study to Define Response and Toxicity

As for specific nerve tolerances to repeat SRS, see: Dose and diameter relationships for facial, trigeminal, and acoustic neuropathies following acoustic neuroma radiosurgery . I have treated in the skull base to 15 Gy for various things, and the risk of facial nerve toxicity is still only about 5% based on the Pitt data. For acoustics I don't usually accept 5% and drop the dose to 12-13 Gy, but for brain mets or certain other scenarios you have to go higher. There is data for SRS retreatment of neuromas and I have done that without any obvious toxicity, so I would just forgive the prior whole brain radiation assuming a good time interval.

 

[scarbrtj]

That's why I wrote that there is no right answer. Everything we're writing is based on opinion, anecdote, and retrospective data.

Is it better to fractionate with a margin or single fraction with no margin? Even if you plan to use an Ikon system to fractionate without a margin, the stereotactic accuracy without a frame is not as good as with a frame. Do you still accept no margin in those cases?

Less than 15-16 Gy does not provide enough control IMO. Brainstem toxicity is real, but death is a bigger problem. Some people with single fraction SRS would argue the other way around and just give 12 Gy to minimize any possible treatment related harm.

For further discussion with the largest series of single fraction plus review of the relevant literature, see: Stereotactic Radiosurgery for Brainstem Metastases: An International Cooperative Study to Define Response and Toxicity

As for specific nerve tolerances to repeat SRS, see: Dose and diameter relationships for facial, trigeminal, and acoustic neuropathies following acoustic neuroma radiosurgery . I have treated in the skull base to 15 Gy for various things, and the risk of facial nerve toxicity is still only about 5% based on the Pitt data. For acoustics I don't usually accept 5% and drop the dose to 12-13 Gy, but for brain mets or certain other scenarios you have to go higher. There is data for SRS retreatment of neuromas and I have done that without any obvious toxicity, so I would just forgive the prior whole brain radiation assuming a good time interval.

Yeah a single shot dose at a dose we’d be willing to give here (previous RT, brainstem, etc) would be infaust for LC and late toxicity trade offs, at least mathematically/on paper. I mean if you were willing to give 20+ Gy single shot, but I bet no one (rightly) would. Forgiving all previous dose definitely opens one’s mind to more aggressive stances. I think sometimes the reason we shoehorn everything to 5 fractions or less here is more billing than medicine.

 

[evilbooyaa]

5Gy x 5 with 1mm Margin on frameless linac-based SRS. Higher risk of necrosis than if she hadn't received WBRT before, but still minimal. Could consider heating up GTV to 6Gy x 5 no margin as long as brainstem point dose could be maintained at some threshold - I would favor brainstem point dose of ~25Gy in this scenario.

 

[Neuronix]

I would favor brainstem point dose of ~25Gy in this scenario.

There is no way that you can prescribe your treatment to 30 Gy with no margin or 25 Gy with 1 mm PTV and have a 25 Gy max point dose given that the tumor is within the brainstem.

 

[evilbooyaa]

There is no way that you can prescribe your treatment to 30 Gy with no margin or 25 Gy with 1 mm PTV and have a 25 Gy max point dose given that the tumor is within the brainstem.

Brainstem - GTV would be my eval structure. Looking at the axial images provided in OP it's right on the edge of the brainstem. Even if only part of the GTV could get 30Gy.

I agree that most likely this patient would end up with 5Gy x 5 given history.

 

[Neuronix]

Brainstem - GTV would be my eval structure. Looking at the axial images provided in OP it's right on the edge of the brainstem. Even if only part of the GTV could get 30Gy.

I agree that most likely this patient would end up with 5Gy x 5 given history.

Falloff from 30 Gy to 25 Gy is about 1-2 mm (depending on a lot of technical details). So if you prescribe to 30 Gy with a 25 Gy brainstem point dose you must not dose the outer part of your met to full dose. I wouldn't call this a 30 Gy treatment. If you dose to 25 Gy with a margin, you're either using Brainstem-PTV as an eval (which I strongly disagree with), or similarly not treating the entire PTV to 25 Gy. I wouldn't call that a 25 Gy treatment either.

When treating with SRS/FSRT, you should be trying to cover at least 99% of the prescription volume with the prescription dose. Where you skimp on dose is where the tumor fails. You can't have a conformity so good that your prescription dose has this level of coverage and doesn't spill to some extent outside of your prescription dose volume.

In summary you can't have your cake and eat it too. You are always balancing control and toxicity in stereotactic brain. I strongly suspect that the variability in how doses are prescribed, delivered, and evaluated accounts for much of differences in outcomes in retrospective series.

 

[scarbrtj]

Falloff from 30 Gy to 25 Gy is about 1-2 mm (depending on a lot of technical details)... You can't have a conformity so good that your prescription dose has this level of coverage and doesn't spill to some extent outside of your prescription dose volume.

There are (spatial) exceptions to every rule. Just as in DVHs, conformity indices contain no inherent spatial information i.e. do not indicate where dose is going. Within the coronal horizontal transverse plane, on brainstem-facing aspect of that tumor, I think I could go from 30->~10 in ~5mm (maybe less mm) by dumping dose superior/inferior/away from stem via beam arrangement/fluences. In this way you might get what on paper looks like a semi-crappy target C.I. but very good brainstem DVH. Semi-crappy target C.I.'s in service of dose-denying an OAR are all the more reason to fractionate.

 

[Neuronix]

Semi-crappy target C.I.'s in service of dose-denying an OAR are all the more reason to fractionate.

Interesting thought. You can do this with single fraction as well--GK (Perfexion or newer) or linac. I have done this in selected cases in the past. Didn't occur to me for this case but not a bad idea to try.

 

[Bequerel]

15-16 Gy in single fraction. Either treat or don’t treat. If your whole goal is to not cause toxicity then just send her to hospice. If you half way palliate her with a 5Gy x 5 fraction regimen, you run a significant risk of being right back here in a few months with a follow up MRI showing progression in the lesion wishing you would have been more aggressive and watching her develop the same side effects you were trying to prevent. Plenty of retrospective data suggesting 15-16 Gy is safe and effective at offering long term local control.

 

[SneakyBooger]

Here is a French perspective:

https://www.redjournal.org/article/S0360-3016(10)00264-6/fulltext

 

[Bequerel]

Here is a French perspective:

https://www.redjournal.org/article/S0360-3016(10)00264-6/fulltext

View attachment 272994

13.4 Gy to 70% IDL is not what I’d consider a “minimized dose”

 

[scarbrtj]

13.4 Gy to 70% IDL is not what I’d consider a “minimized dose”

Especially in the brainstem (max dose ~19 Gy).
Is normofractionating to a large-ish dose super stupid here? Probably. Or no? I remember in START where they said breast α/β had 95% confidence interval of 1 to 8. If we ignore her previous dose...
................................... Tumor BED 60/30................. Tumor BED 15/1..................
α/β tumor=1........................120 ...............................................240....................15/1 100% hotter
α/β tumor=8.........................75...................................................43......................60/30 74% hotter
Late effects(α/β=2).............120................................................128....................15/1 7% hotter
Depending on where her tumor lies on the α/β spectrum, 15/1 could be the right choice... or the wrong choice. One could make the not ill-informed guess that her tumor α/β might be on the higher end of 1 to 8. Maybe this is why we see such variable outcomes patient-to-patient (ie tumor-to-tumor) in SRS. We may debate BEDs at high fraction sizes for tumor effects but I think late effect prediction power is still pretty useful. Just personally, I would predict 0% local control long term for a similar sized metastatic lesion in the lung with 15/1. When breast cancer travels to brain, does it become more radiosensitive?

 

[Palex80]

Most has been said already in this thread.


The debate focuses on two objects:

1. Dose per fraction / fractionation
My personal view in these cases is to try to fractionate, bearing in mind that rates of necrosis are lower with fractionation than with single-shot radiosurgery (at least from what we know in bigger lesions - 3x9Gy vs. 1x20Gy - Single-Fraction Versus Multifraction (3 × 9 Gy) Stereotactic Radiosurgery for Large (>2 cm) Brain Metastases: A Comparative Analysis of Local Contr... - PubMed - NCBI ). Thus in a patient who has already had some dose to that region and this reason being an eloquent one, I presume that fractionation is a good idea. Giving radiosurgery is always an option, but if you stay too low with those dose, it's probably better to fractionate. If you end up giving "only" 12 Gy marginal dose to this patient with an SRS and 0 mm margin, you are not going to succeed in controlling this lesion long-term wise. I would feel more comfortable with something like 6 x 5 Gy or 9 x 4 Gy with not more than 100% of the dose in the brainstem, if you want to play it "safer" 5 x 5 Gy or 7 x 4 Gy appear promising too.

2. Margin / Immobilisation
There are believers and not-believers here as well. We know that a margin of 0mm is probably not a good idea. It doesn't necessarily have to do with immobilisation, you also need to weigh in all the factors. Your CBCT is also not 0mm accurate, your couch may also not be 100% stable, there may be rotational errors, your QA is also not 100% accurate, the same applies to your contouring and your fusion and last but not least there are tumor cells beyond the edge of the contrast enhancement on the MRI. I feel confident with 1mm GTV-CTV-margin in SRS and add 1mm for CTV-PTV-margin when we use mask immobilisation. There is data supporting this approach: https://www.ncbi.nlm.nih.gov/pubmed/20951506; Radiosurgery for brain metastasis: impact of CTV on local control. - PubMed - NCBI
But you shouldn't overdo the margin either: Defining the optimal planning target volume in image-guided stereotactic radiosurgery of brain metastases: results of a randomized trial. - PubMed - NCBI
In this special occasion we are talking about brainstem. I would thus "drop" the 1mm GTV-CTV-margin, since that would imply drawing the CTV in the brainstem. I would however still keep the 1mm CTV-PTV-margin.

 

[SneakyBooger]

Here is a study that has a nice discussion of brainstem mets.

Seems some series used rather lower than "normal" marginal doses with good results.

 

[Palex80]

Indeed, the Samblas-article shows high rate of PFS with 11.1 Gy marginal dose HOWEVER it seems that practically all patients also had WBRT.

I don't have access to the full paper, but it seems the WBRT was delivered together with the SRS (before or after it). It is thus highly likely that the dose of the SRS was limited to 11.1 Gy exactly because the treating physicans delivered WBRT together with the SRS as one treatment course. I would never give 30/3 WBRT and a 16Gy SRS on top as one course.


Whether or not the dose of 11.1 Gy is efficient enough in patients
a) who have had PRIOR WBRT and now have a brainstem recurrence or
b) never had WBRT (and are not scheduled to undergo one)

is a totally different question.


You can actully see in the paper you quoted that in those series where WBRT was not delivered (or only delivered in a few patients) marginal doses are generally higher than in those where WBRT was given.

 

[scarbrtj]

If you believe in "The Wisdom of Crowds" by James Surowiecki, and you average up all the dose/fractions offered thus far in this thread...
you get as the correct answer for this patient: 26 Gy in 5 fractions.

 

[xrthopeful]

25/5 is a dose we use for benign things intracranially. I don’t see the point of using it here.

 

[scarbrtj]

25/5 is a dose we use for benign things intracranially. I don’t see the point of using it here.

25 Gy in 5 fractions can achieve a pCR in ~25% of rectal cancer patients. It's not nothing. It may not make cancer quake in its boots but it definitely makes it think about its choices in life.

 

[xrthopeful]

The pCR rate of 25 percent is also with a bunch of upfront chemo as part of a TNT approach, not necessarily a fair comparison

 

[SneakyBooger]

Full Samblas article (pdf) can be found here:

https://www.researchgate.net/publication/38010891_Radiosurgery_and_whole_brain_therapy_in_the_treatment_of_brainstem_metastases

 

[scarbrtj]

The pCR rate of 25 percent is also with a bunch of upfront chemo as part of a TNT approach, not necessarily a fair comparison

Who said I made fair comparisons

 

[scarbrtj]

I would never give 30/3 WBRT and a 16Gy SRS on top as one course.

Why would you never do that. We (me?) used to do it a lot.* It--WBRT plus SRS boost--was once a standard of care. I might argue it still might be to some extent, in certain situations. At least a tool in the toolbox so to speak. One thing that's a little surprising is when you look back at stuff like this... 37.5 Gy whole brain plus SRS boosts... failure was still as high as 20% at 1 year. Something like 37.5 Gy whole brain plus a ~20Gy SRS boost is a hefty dose. And yet there's data saying ~13 Gy in single shots (see what somebody posted above) gets the same local control. Go figure.
*granted not often in brainstem

Full Samblas article (pdf) can be found here:

https://www.researchgate.net/publication/38010891_Radiosurgery_and_whole_brain_therapy_in_the_treatment_of_brainstem_metastases

Also one could make the argument... there are no hard and fast rules here that I know of... that this lady doesn't have a brainstem met from the standpoint of being as "reverential" as we are toward the brainstem. It's off in the peduncle for the most part. Her CN VII problem isn't from CN VII nucleus involvement most likely, just only because the lesion or its edema is glancing the facial fibers as they recur and loop around, out, and laterally from the back of the brainstem. So really, neurologically, her CN toxicity is due to involvement of peripheral nerve fibers instead of central nervous system fibers. Pedantic. But, her brainstem DVH is going to look much better than the typical brainstem met patient. This won't be due to the planner's superiority, it will be due to anatomy.

 

[SneakyBooger]

More brainstem to think about:

 

[Pointless]

25/5 is a dose we use for benign things intracranially. I don’t see the point of using it here.

Just because something is used for one thing, doesn't necessarily mean its not effective for another thing. I have used 5 x 5 for brainstem mets in situations like this with good effect. In most cases, the prognosis is quite poor and thus you have to consider that your main priority in a case like this is to first do no harm. 5 x 5 is more than a whole brain dose, so certainly not nothing, but also not cavalier.

 

[Ray D. Ayshun]

25/5 is a dose we use for benign things intracranially. I don’t see the point of using it here.

I thought benign things are more radioresistant than malignant things.

 

[Palex80]

Why would you never do that. We (me?) used to do it a lot.* It--WBRT plus SRS boost--was once a standard of care. I might argue it still might be to some extent, in certain situations. At least a tool in the toolbox so to speak. One thing that's a little surprising is when you look back at stuff like this... 37.5 Gy whole brain plus SRS boosts... failure was still as high as 20% at 1 year. Something like 37.5 Gy whole brain plus a ~20Gy SRS boost is a hefty dose. And yet there's data saying ~13 Gy in single shots (see what somebody posted above) gets the same local control. Go figure.
*granted not often in brainstem

Well u said it yourself: Not brainstem. Other than that, sure.

 

[SneakyBooger]

How about SRT?

Local control after fractionated stereotactic radiation therapy for brain ...dunnlab.bwh.harvard.edu/.../Rajakesari-2014-localized-control-after-stereotactic-radio...

 

[xrthopeful]

local control at 1 year of 56% doesn't speak super highly of 25/5 as a brain met dose IMO.

 

[SneakyBooger]

From same study:

How about SRT?

Local control after fractionated stereotactic radiation therapy for brain ...dunnlab.bwh.harvard.edu/.../Rajakesari-2014-localized-control-after-stereotactic-radio...

View attachment 273167

View attachment 273168

 

[xrthopeful]

I'm not sure when that survey is from or who participated. I agree there may be certain situations where you feel like you need to lower the dose, but 25/5 IMO should not be a routine fractionated SRS brain metastasis dose.

 

[evilbooyaa]

15-16 Gy in single fraction. Either treat or don’t treat. If your whole goal is to not cause toxicity then just send her to hospice. If you half way palliate her with a 5Gy x 5 fraction regimen, you run a significant risk of being right back here in a few months with a follow up MRI showing progression in the lesion wishing you would have been more aggressive and watching her develop the same side effects you were trying to prevent. Plenty of retrospective data suggesting 15-16 Gy is safe and effective at offering long term local control.

Nothing wrong with 5Gy x 5 when comparing it to 15Gy single fraction. They both have the exact same BED10 of 37.5. I get not doing 5Gy x 5 in favor of more aggressive dosing like 9x3 or 18-24x1, but to say do 15x1 instead is silly.

Again, if it wasn't a brainstem met in a patient who had previously had WBRT I don't think anybody is doing 5Gy x 5. Let's try to focus on the clinical situation, not just espouse data on all brain mets in general.

 

[SneakyBooger]

Question for all:

How do you differentiate radionecrosis from recurrence in the brainstem?

Example:

What do you call it if pt gets 17Gy for 0.8 cm brainstem met and 4 months later they begin rapid neurological decline with an MRI showing increasing vasogenic edema and slight increase in marginal enhancement with central necrosis and then they die at month 5 - do you call it recurrence or RT necrosis or pseudoprogression or what? And maybe there are 12 new lesions.

If my buddy the neuroSx asks me, or my buddy the neurorad, I say it is death due to distant progression and count it as local control?

 

[SneakyBooger]

I'm not sure when that survey is from ...

Arvold ND, Pinnell NE, Mahadevan A et al (2012) Physician recommendations for steroid and anticonvulsant use following stereotactic radiosurgery. Int J Radiat Oncol Biol Phys 84:S292–S293

 

[Pointless]

I'm not sure when that survey is from or who participated. I agree there may be certain situations where you feel like you need to lower the dose, but 25/5 IMO should not be a routine fractionated SRS brain metastasis dose.

Not routine at all. This is a brainstem lesion in a previously radiated patient... quite the opposite of routine. That study you quoted with the 56% control rate... it's a retrospective series in which some patients got 30 in 10. Not that I really care, but did they break down LC by fractionation?

Anyway, everyone is free to do as they see fit. Perhaps I err conservative, but I would be looking not to melt this person's brainstem... I hear those are important for stuff.

 

[xrthopeful]

Not routine at all. This is a brainstem lesion in a previously radiated patient... quite the opposite of routine. That study you quoted with the 56% control rate... it's a retrospective series in which some patients got 30 in 10. Not that I really care, but did they break down LC by fractionation?

Anyway, everyone is free to do as they see fit. Perhaps I err conservative, but I would be looking not to melt this person's brainstem... I hear those are important for stuff.

1) I was replying to Sneaky saying that 25/5 was the most commonly used SRT dose in that survey. That doesn't jive with common practice in 2019 for me. Does it for you? I'm not saying THIS case is routine, I'm saying that 25/5 should not be the most commonly used routine dose, as that survey apparently suggests

2) They did say that 25/5 was used in that RR series in 87% of patients, so the vast majority of patients that contributed to the local control rate.

 

[Bequerel]

I think those of us who have been in practice long enough realize that 5Gy x 5 is SBRT-lite. It is not a commonly used aggressive palliative fractionation and is likely used more to meet the minimum of an arbitrary reimbursement definition of SBRT.

 

[scarbrtj]

I think those of us who have been in practice long enough realize that 5Gy x 5 is SBRT-lite. It is not a commonly used aggressive palliative fractionation and is likely used more to meet the minimum of an arbitrary reimbursement definition of SBRT.

Sad but true. So true.
EDIT: I’m being funny, but for those outside rad onc or those interested in it, this is not funny: in the US a lot of rad onc practice and standards are not really set by the rad onc community but instead by as Bq says “arbitrary” definitions of what some significant rad onc things are by the government. Private insurance then accepts the government standard. For example, the government and not the scientific literature has decided, far in advance of the science or clinical practices becoming mature, what IMRT and SBRT are/are not. And not the other way around. A little sensationalist, but a lot like Newspeak from “1984.”

 

[Pointless]

I think those of us who have been in practice long enough realize that 5Gy x 5 is SBRT-lite. It is not a commonly used aggressive palliative fractionation and is likely used more to meet the minimum of an arbitrary reimbursement definition of SBRT.

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.

 

[scarbrtj]

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.

Wellllllllllllll... any time one considers 5 x 5 for re-XRT, it might cross one's mind for a brief split second, "What about 6 times 4.25?" And then like the wind that thought would be gone. Gone baby gone. EDIT: reminds me of the old "corner blocks" in rad onc. Ah those were the days only pre-3D era rad onc experiencers will get that joke maybe (and TBH, the 6 fraction high dose per fraction regimen is a jackalope)