Your favorite spine SRS/SBRT regimen

[Mandelin Rain]

I know, I know, I know 8Gy in 1.

I'm talking sole site of metastatic disease in an otherwise high performing patient. Not just pain relief.

Thinking of switching to fractionated from single fraction SRS, mainly due to compression fracture risk. Anyone have a recipe they feel strongly about?

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[thecarbonionangle]

9x3, 10x3

 

[Neuronix]

If it's a straightforward case 16-18 Gy x 1 fraction using consensus guidelines (https://www.redjournal.org/article/S0360-3016(12)00367-7/pdf).

Radioresistant I will consider dose painting higher to the gross disease up to 24 Gy.

I don't understand 3 fraction at all. If you think fractionation helps, give 5. If you're worried about number of fractions, just give 1.

For five fraction I usually do 35 Gy x 5 fractions. I usually do this for the tougher cases, so I often have to dose paint down at the cord.

 

[thecarbonionangle]

If it's a straightforward case 16-18 Gy x 1 fraction using consensus guidelines (https://www.redjournal.org/article/S0360-3016(12)00367-7/pdf).

Radioresistant I will consider dose painting higher to the gross disease up to 24 Gy.

I don't understand 3 fraction at all. If you think fractionation helps, give 5. If you're worried about number of fractions, just give 1.

For five fraction I usually do 35 Gy x 5 fractions. I usually do this for the tougher cases, so I often have to dose paint down at the cord.

im curious why you think 3 fx is worst than 5. 5 is fine too. I know the linear quad formula breaks down, but they have similar BEDs/EQD2s

 

[taserlaser]

Personally a fan of the 24 / 2 regimen. High dose to tumor, lower compression fracture risk than single fraction.

https://www.redjournal.org/article/S0360-3016(18)31048-4/pdf

 

[Mandelin Rain]

Those three posts beautifully capture the reason I posted this question

1 x 16 Gy
1 x 18 Gy
1 x 24 Gy
2 x 12 Gy
3 x 9 Gy
3 x 10 Gy
5 x 7 Gy

I was liking the idea of 2 x 12 or 3 x 9 before, again, mainly to lower the risk of compression fracture rather than any tumor specific effect.

 

[RadOncMegatron]

For SBRT spine multi fractionation, what set up do you guys use? SBRT frame? Ok to do without 6D couch? If no couch do 3?5? Asking for a friend

 

[KHE88]

Some weird 8 fraction "IMRT" plan in the 40-45 Gy range because Evicore wouldn't approve 5 fraction SBRT.

I prefer 27 in 3 or 24 in 2. Don't like single fraction personally.

 

[CptCrunch]

27 in 3

 

[evilbooyaa]

27 in 3 or 30-35/5.

Depends on extent of epidural disease. If none can push more for 27 in 3.

 

[Palex80]

Personally a fan of the 24 / 2 regimen. High dose to tumor, lower compression fracture risk than single fraction.

Precisely!
Do you use Dmax 2 x 8.5 Gy for spinal cord?

What I have been discussing with colleagues is the target volume definition issue.
Contouring guidelines call for a rather large CTV. For example with a 1cm well lateralized lesion in the vertebral body you should still contour the entire vertebral body as a CTV and prescribe the dose to it.
Sorry for my bad MS Paint skills...

Green is GTV, you can make it bigger if you want to.
Red is the cropped CTV, I didn't add the pedicle here but you could probably add it to depending on how close the GTV goes to the edge of the vertebra.

Do you feel that the risk of microscopic tumor for example in the purple area which is something like 1.5-2 cm away from the GTV is high enough to justify that area receiving the full dose?
Wouldn't it be better to prescribe a higher dose to the GTV with a small PTV margin and then cover the rest of the CTV (as per recommendation) with a lower dose? In other words: why should macroscopic disease receive the same dose as microscopic disease? Could such an approach perhaps lower the risk for fracture.

Now, this is pretty "simple" case, where the lesion is well confined. Certainly in a bigger lesions involving most of the vertebra or when you cannot really see its boundaries well even with a good MRI, I understand that declaring a part of the vertebra as "uninvolved" may be difficult, but what about cases of small mets like this one?

 

[Palex80]

27 in 3

Constraint for spinal cord?
3 x 6.5 Gy?

 

[scarbrtj]

Those three posts beautifully capture the reason I posted this question

1 x 16 Gy
1 x 18 Gy
1 x 24 Gy
2 x 12 Gy
3 x 9 Gy
3 x 10 Gy
5 x 7 Gy

I was liking the idea of 2 x 12 or 3 x 9 before, again, mainly to lower the risk of compression fracture rather than any tumor specific effect.

Wisdom of Crowds answer on everyone's input is something like 28 Gy/2 fx... an interesting regimen!

 

[CptCrunch]

Constraint for spinal cord?
3 x 6.5 Gy?

We use TG 101, Dmax < 22 Gy total

 

[CptCrunch]

Precisely!
Do you use Dmax 2 x 8.5 Gy for spinal cord?

What I have been discussing with colleagues is the target volume definition issue.
Contouring guidelines call for a rather large CTV. For example with a 1cm well lateralized lesion in the vertebral body you should still contour the entire vertebral body as a CTV and prescribe the dose to it.
Sorry for my bad MS Paint skills...

Green is GTV, you can make it bigger if you want to.
Red is the cropped CTV, I didn't add the pedicle here but you could probably add it to depending on how close the GTV goes to the edge of the vertebra.
View attachment 308900
Do you feel that the risk of microscopic tumor for example in the purple area which is something like 1.5-2 cm away from the GTV is high enough to justify that area receiving the full dose?
Wouldn't it be better to prescribe a higher dose to the GTV with a small PTV margin and then cover the rest of the CTV (as per recommendation) with a lower dose? In other words: why should macroscopic disease receive the same dose as microscopic disease? Could such an approach perhaps lower the risk for fracture.

Now, this is pretty "simple" case, where the lesion is well confined. Certainly in a bigger lesions involving most of the vertebra or when you cannot really see its boundaries well even with a good MRI, I understand that declaring a part of the vertebra as "uninvolved" may be difficult, but what about cases of small mets like this one?

This is an interesting question and I'm interested in what others would do. I also wonder if microscopic disease should receive the same dose as microscopic disease. In these situations with a small, well-defined lesion, I have used SIB to deliver 9-10 Gy x 3 to the GTV + 3mm margin and treating the rest of the CTV to 8 Gy x 3.

 

[evilbooyaa]

This is an interesting question and I'm interested in what others would do. I also wonder if microscopic disease should receive the same dose as microscopic disease. In these situations with a small, well-defined lesion, I have used SIB to deliver 9-10 Gy x 3 to the GTV + 3mm margin and treating the rest of the CTV to 8 Gy x 3.

Agreed. If I can't make 9Gy x 3 work for the whole CTV (besides dose painting away from cord), I'll try to ensure at least GTV gets that.

 

[Mandelin Rain]

Agreed. If I can't make 9Gy x 3 work for the whole CTV (besides dose painting away from cord), I'll try to ensure at least GTV gets that.

Hypofractionated Stereotactic Body Radiotherapy in Spinal Metastasis — With or Without Epidural Extension

To evaluate clinical outcome and the effect of malignant epidural compression (MEC) in the treatment of spine metastasis with stereotactic body radiot…

www.sciencedirect.com

Good description of just that.

 

[Neuronix]

mainly to lower the risk of compression fracture rather than any tumor specific effect.

Is there any evidence that fractionated lowers compression fraction risk for the same adjusted BED? The risk is pretty low at 16-18 Gy x 1 regardless.

 

[RickyScott]

Is there any evidence that fractionated lowers compression fraction risk for the same adjusted BED? The risk is pretty low at 16-18 Gy x 1 regardless.

Haven’t looked at the data in a while, but didn’t the group in torronto find more fractures with single dose? I just feel more comfortable averaging out possible errors with 3 treatments?

 

[Palex80]

Is there any evidence that fractionated lowers compression fraction risk for the same adjusted BED? The risk is pretty low at 16-18 Gy x 1 regardless.

This recent metaanalysis points at higher risk with single fraction treatments.

Single fraction radiosurgery, fractionated radiosurgery, and conventional radiotherapy for spinal oligometastasis (SAFFRON): A systematic review and meta-analysis - PubMed

SF-SRS resulted in superior LC with a roughly 5% LC benefit for every 10 Gy₁₀ increase in BED₁₀ with higher VCF rates compared to MF-SRS. If LC is the goal of treatment, then SRS may be a preferred treatment modality. However, these results are hypothesis-generating, and...

pubmed.ncbi.nlm.nih.gov

However, as you say, this analysis was not adjusted for BED.
So indeed, 1 x 20 Gy may produce more fractures than 2 x 12 Gy, but the BED of 1 x 20 Gy is also higher than 2 x 12 Gy.

 

[Mandelin Rain]

I think there is quite a bit of data that CF rate is higher in single fraction than fractionated. Not controlled for BED, to my knowledge.

 

[Neuronix]

A lot of people tried to push into the 20s in 1 fraction and got more compression fracture risk at 20+ Gy (https://ascopubs.org/doi/full/10.1200/JCO.2013.50.1411). 20 Gy in 1 fraction is a higher BED than 3x10 Gy assuming alpha/beta=2. I don't see anyone going higher than 3x10 Gy, and most stop at 3x9 Gy.

Here's the problem though: 3x9 Gy is about the same BED as 1x16 Gy with alpha/beta=2. Fracture risk at 1x16 Gy is pretty low. The paper linked from Palex shows less local control with either of 3x9 Gy and 1x16 Gy compared to higher dose.

The paper linked indicates "Among all studies examined, we did not find that higher BED10 was associated with statistically significant increased incidence of VCF (p = 0.33; Supplementary Fig. 5)." Also, Palex's paper indicates 9.6% for MF-SRS which is basically the same rate as the paper I just linked for doses less than 20 Gy.

So this paper's conclusion is misleading IMO. If you push doses higher, you increase compression fracture risk. More people have tried to push higher with single fraction than with fractionated.

I personally don't like the argument that 3 fraction is safer because it "averages out errors". I try to set these up very precisely and watch everything like a hawk. Whether I do single fraction or multi-fraction, I am super on top of these cases and don't even want to think that an error might occur. I'd rather give one very precise treatment rather than several very precise treatments.

One thing I have noticed: the technical reimbursements are higher for fractionated SBRT compared to single fraction.

 

[scarbrtj]

One thing I have noticed: the technical reimbursements are higher for fractionated SBRT compared to single fraction.

Of course. Rare to find any patients at Cyberknife centers e.g. who get less than 5 fractions. #NoJudgment
This is the sound your biller hears when you do "SBRT" in 6 or more fractions.

 

[Burt Radnolds]

How are you all defining the cord that you use for constraints? MRI cord? MRI cord +2mm?

 

[medgator]

One thing I have noticed: the technical reimbursements are higher for fractionated SBRT compared to single fraction.

Same as other radiation modalities, that's how our specialty is reimbursed in general....

 

[ramsesthenice]

What is the rationale for treating the entire vertebral body for a small, lateralized lesion? Is the whole vertebral really at risk of microscopic disease? Or is the concern that it would be hard to go back if they fail?

 

[Gfunk6]

What is the rationale for treating the entire vertebral body for a small, lateralized lesion? Is the whole vertebral really at risk of microscopic disease? Or is the concern that it would be hard to go back if they fail?

As I understand it, if you treat a small portion of the body with an ablative dose you increase the risk of an asymmetric fracture. This is mitigated by treated the whole body.

 

[Palex80]

As I understand it, if you treat a small portion of the body with an ablative dose you increase the risk of an asymmetric fracture. This is mitigated by treated the whole body.

And is there any data to support that assumption?

 

[Neuronix]

What is the rationale for treating the entire vertebral body for a small, lateralized lesion? Is the whole vertebral really at risk of microscopic disease? Or is the concern that it would be hard to go back if they fail?

The rationale given here is

International Spine Radiosurgery Consortium consensus guidelines for target volume definition in spinal stereotactic radiosurgery - PubMed

This report provides consensus guidelines for target volume definition for spinal metastases receiving upfront SRS in common clinical situations.

pubmed.ncbi.nlm.nih.gov

"Patterns of failure analysis have identified marginal failures beyond the conformal targeted volume as a primary pattern of recurrence (19, 20), "

 

[KHE88]

I have always wondered this as well. Especially for say, a well lateralized transverse process lesion. Do we really need to cover the entire vertebral body with no radiographic evidence of disease there? We are told that the intervertebral discs are barriers to spread. So it that regard it makes since to treat the entire spinal level. But at the same time, there are a non-insignificant number of rad oncs who palliative "one above and below" because of worry of spread (I don't do this). Are they just flat out wrong? It would certainly be harder to retreat the same spinal level that was partially treated before with SBRT. The guidelines of course specify exactly how much of the vertebral body to treat, and I'm not sure where this comes from, but I follow the guidelines and have not seen any out-of-field same-vertebrae failures in my training or short career.

 

[Neuronix]

But at the same time, there are a non-insignificant number of rad oncs who palliative "one above and below" because of worry of spread (I don't do this). Are they just flat out wrong?

I would argue yes, but there are still reasons to do it that way.
1. When doing AP-PA you can't make a reasonable field by making your superior and inferior field borders the top and bottom of that vertebral level. The field is so small that the dose becomes very non-uniform across the target. You always have to go higher and lower to get full dose at that level.
2. People in the past always avoided "splitting levels" so that they could match at the interspace later. It's a lot easier to match that way than match in the middle of a bone.
3. In the old days of light field or MV, I think getting the level wrong was more common than people would admit to. It can be really hard to tell what level you're at on a port film of the T-spine. Going one above and below gives a fudge factor.
4. It's really simple and fast to just tell dosimetry to throw fields on at a level (or give the borders)

With IMRT this whole discussion kind of becomes moot, but you're not going to get IMRT approval for every simple palliative case. Palex over there in Europe will probably be around in a few minutes to laugh about this.

If you want to do 3D IMRT-lite to just one vertebral level, you can contour it out and do a 3D arc plan. I do this sometimes.

 

[scarbrtj]

We are told that the intervertebral discs are barriers to spread.

Sometimes you wonder, do people really get properly critical of the dogma. It is well accepted that mets spread hematogenously. So put another way, the statement "We are told that the intervertebral discs are barriers to spread" is like saying "We are told that the intervertebral discs are barriers to the bloodstream."

 

[Neuronix]

Sometimes you wonder, do people really get properly critical of the dogma. It is well accepted that mets spread hematogenously. So put another way, the statement "We are told that the intervertebral discs are barriers to spread" is like saying "We are told that the intervertebral discs are barriers to the bloodstream."

Barriers to local spread. We're doing radiotherapy here for local control, so I thought that was implied.

Of course that's not 100%. Watch out for extraosseous extention that can absolutely locally spread sup-inf. I've seen those failures for sure.

 

[evilbooyaa]

I have always wondered this as well. Especially for say, a well lateralized transverse process lesion. Do we really need to cover the entire vertebral body with no radiographic evidence of disease there? We are told that the intervertebral discs are barriers to spread. So it that regard it makes since to treat the entire spinal level. But at the same time, there are a non-insignificant number of rad oncs who palliative "one above and below" because of worry of spread (I don't do this). Are they just flat out wrong? It would certainly be harder to retreat the same spinal level that was partially treated before with SBRT. The guidelines of course specify exactly how much of the vertebral body to treat, and I'm not sure where this comes from, but I follow the guidelines and have not seen any out-of-field same-vertebrae failures in my training or short career.

I still cover entire vertebral body although will consider allowing uninvolved bone a far distance away to get lower than prescription dose if OARs are an issue.

It's a good question but everything in terms of spine SBRT contouring is done as an extrapolation of how things were done palliatively (where you always cover entirety of vertebral body) and was guided, from the beginning, by 'international guidelines' meaning "some dudes in a room expert opinions" and not data driven. Usually minimal harm to doing so FWIW.

Neuronix has described the one above and one below thing better, but to answer the bolded, yes, they are wrong. There are reasons to 1 above and 1 below (and I still do for 3D palliation given beam penumbra issues) but worrying about local cancer spread in the absence of extraosseus paraspinal extension of disease is not one of those reasons.

 

[KHE88]

Sometimes you wonder, do people really get properly critical of the dogma. It is well accepted that mets spread hematogenously. So put another way, the statement "We are told that the intervertebral discs are barriers to spread" is like saying "We are told that the intervertebral discs are barriers to the bloodstream."

Sometimes I wonder if you are being deliberately obtuse. By that logic, treating one above and below is not enough, we should just do TBI palliation.
The discs are barriers to local spread. How many times have you seen a tumor grow through a disc into the adjacent level?

Agree with Neuronix. For palliation, I like to cover the entire vetebral body with near prescription dose if possible. This means extending non-trivial dose to a decent portion of adjacent levels. Of course treating one above and below would still some dose into levels two above two below. Are we more likely to have to come back and treat one above than two above in the future? Maybe, but I don't care. Even a lowlevel cowtown nobody like me can get evicore to approve spine SBRT in the setting of pain and prior radiation.

 

[scarbrtj]

Sometimes I wonder if you are being deliberately obtuse. By that logic, treating one above and below is not enough, we should just do TBI palliation.
The discs are barriers to local spread. How many times have you seen a tumor grow through a disc into the adjacent level?

Haha deliberate obtuseness: def the worst of the obtusities. No I'm saying there's roughly three XRT worries:
1) Worries about the things we can see
2) Worries about the things we can't see (generally nearby the things we can see)
3) Non-worry about the things we can't see
In the setting of metastatic disease, I'm almost exclusively #1. (It may look like, if you saw my tx techniques, I'm throwing in #2 CTV-like, but usually it's for expediency/easiness/tradition if so.)

Watch out for extraosseous extention that can absolutely locally spread sup-inf. I've seen those failures for sure.

How many times have you seen a tumor grow through a disc into the adjacent level?

The question is, was this failure of therapy on the lesion you could see, or failure to irradiate nearby cancer cells we couldn't see. I think it's much more the former.

 

[evilbooyaa]

Sometimes I wonder if you are being deliberately obtuse. By that logic, treating one above and below is not enough, we should just do TBI palliation.
The discs are barriers to local spread. How many times have you seen a tumor grow through a disc into the adjacent level?

Agree with Neuronix. For palliation, I like to cover the entire vetebral body with near prescription dose if possible. This means extending non-trivial dose to a decent portion of adjacent levels. Of course treating one above and below would still some dose into levels two above two below. Are we more likely to have to come back and treat one above than two above in the future? Maybe, but I don't care. Even a lowlevel cowtown nobody like me can get evicore to approve spine SBRT in the setting of pain and prior radiation.

We don't treat the entirety of the level below and level above to prescription dose. We put block edges there to ensure the target vertebral body gets prescription dose. This leads to 5-7mm edges getting less than prescription dose while completely sparing vertebral bodies 2 above and 2 below.

If we're treating T9, the inferior block edge is at the inferior aspect of T10, the superior block edge is at the superior aspect of T8.

 

[Neuronix]

The question is, was this failure of therapy on the lesion you could see, or failure to irradiate nearby cancer cells we couldn't see. I think it's much more the former.

I agree with that. There's always dose fall off to treat microscopic disease if you're going to high doses like SBRT. The real issue IMO is: did you get an MRI? Was it a decent quality MRI? Was it fused well? Do you know how to interpret that spine MRI? For intrasosseous disease, you can see bone very easily on CT, that's usually not much of an issue. You may miss or underestimate the extention out of the bone without at least IV contrast, but really you need a good and very recent MRI.

Of course if you throw a giant field on, you won't miss. Local control becomes more of an issue with 30 Gy in 10 fractions to a big field. Marginal miss becomes more of an issue with 18 Gy in 1 fraction to a tight field.

 

[Gfunk6]

And is there any data to support that assumption?

Great question. I looked into the published recommendations re: spine radiosurgery by the International Spine Radiosurgery Consortium (ISRC), published in the red journal in 2012.

Link: International Spine Radiosurgery Consortium Consensus Guidelines for Target Volume Definition in Spinal Stereotactic Radiosurgery - PubMed

Here is the rationale they used to treat the spine in discrete sectors rather than just the GTV.

Consensus contours be made using a modified Weinstein-BorianiBiagini system for spine tumor staging (24). This is a standardized staging system that has been widely adopted in the neurological and orthopedic surgical literature to facilitate surgical planning and communication of results from en bloc vertebrectomy. It was the opinion of the task force that dividing each vertebral body into 12 sectors, as done in the Weinstein-Boriani-Biagini system, would be unwieldy for consensus contour recommendations. Therefore, the modified system proposed here divides each vertebral body into 6 sectors, as shown in Fig. 1. Sector 1 represents the vertebral body, sector 2 represents the left pedicle, sector 3 represents the left transverse process and lamina, sector 4 represents the spinous process, sector 5 represents the right transverse process and lamina, and sector 6 represents the right pedicle.

So it sounds like it was based using analogous principles for spine surgery rather than vertebral body fracture risk.

 

[ramsesthenice]

So in short what we have is 90% rationale and 10% data? Not trying to sound obtuse, just clarifying.

As to the one above one below 3D question, Neuronix is spot on. Look at a 10x10 cm MV port film in the mid thoracic spine and tell me how confident you are that you are looking at T3-T7 and not T4-T8 (or even T5-T9). That discussion has no relevance to modern SBRT.

 

[RickyScott]

Precisely!
Do you use Dmax 2 x 8.5 Gy for spinal cord?

What I have been discussing with colleagues is the target volume definition issue.
Contouring guidelines call for a rather large CTV. For example with a 1cm well lateralized lesion in the vertebral body you should still contour the entire vertebral body as a CTV and prescribe the dose to it.
Sorry for my bad MS Paint skills...

Green is GTV, you can make it bigger if you want to.
Red is the cropped CTV, I didn't add the pedicle here but you could probably add it to depending on how close the GTV goes to the edge of the vertebra.
View attachment 308900
Do you feel that the risk of microscopic tumor for example in the purple area which is something like 1.5-2 cm away from the GTV is high enough to justify that area receiving the full dose?
Wouldn't it be better to prescribe a higher dose to the GTV with a small PTV margin and then cover the rest of the CTV (as per recommendation) with a lower dose? In other words: why should macroscopic disease receive the same dose as microscopic disease? Could such an approach perhaps lower the risk for fracture.

Now, this is pretty "simple" case, where the lesion is well confined. Certainly in a bigger lesions involving most of the vertebra or when you cannot really see its boundaries well even with a good MRI, I understand that declaring a part of the vertebra as "uninvolved" may be difficult, but what about cases of small mets like this one?

Agree with you. in cases of re-treatment, I only cover gtv with margin.

 

[Neuronix]

So in short what we have is 90% rationale and 10% data? Not trying to sound obtuse, just clarifying.

Basically. The same group published sacral consensus guidelines in green journal recently. That one is 100% rationale and 0% data IMO.

 

[BobbyHeenan]

Personally a fan of the 24 / 2 regimen. High dose to tumor, lower compression fracture risk than single fraction.

https://www.redjournal.org/article/S0360-3016(18)31048-4/pdf

Do you treat on consecutive days or separate by a day or two?

 

[taserlaser]

Do you treat on consecutive days or separate by a day or two?

I asked the same question to those in the group, and they told me they treat consecutive to try and optimize tumor control. I personally don’t think it would be wrong to do it with a day or two in between though, as sometimes these patients can get a pain flair.

 

[scarbrtj]

I asked the same question to those in the group, and they told me they treat consecutive to try and optimize tumor control. I personally don’t think it would be wrong to do it with a day or two in between though, as sometimes these patients can get a pain flair.

am I hallucinating or did someone somewhere analyze qd vs qod and find qd had LESS local control in an SBRT setting

 

[taserlaser]

am I hallucinating or did someone somewhere analyze qd vs qod and find qd had LESS local control in an SBRT setting

Would be really interested to see such an analysis - I’ve not heard of this. Might have to go hunting for that data myself over the weekend to feed my own curiosity.

 

[FrostyHammer]

am I hallucinating or did someone somewhere analyze qd vs qod and find qd had LESS local control in an SBRT setting

https://www.thegreenjournal.com/article/S0167-8140(16)31245-2/abstract

 

[taserlaser]

https://www.thegreenjournal.com/article/S0167-8140(16)31245-2/abstract

Big difference. Thanks for the reference.

 

[evilbooyaa]

https://www.thegreenjournal.com/article/S0167-8140(16)31245-2/abstract

Although is opposite of the CCF/Wash U experience suggesting no difference in LC on pooled retrospective analysis: Local Control for Clinical Stage I Non-Small Cell Lung Cancer Treated With 5-fraction Stereotactic Body Radiation Therapy Is Not Associated With Treatment Schedule - PubMed

Also data to suggest QOD is less toxic (which most could probably imagine) in lung SBRT at least.

Influence of Fractionation Scheme and Tumor Location on Toxicities After Stereotactic Body Radiation Therapy for Large (≥5 cm) Non-Small Cell Lung Cancer: A Multi-institutional Analysis - PubMed

From this multi-institutional study, toxicity of SBRT for ≥5-cm lesions is acceptable, and daily treatment was associated with a higher rate of toxicities.

pubmed.ncbi.nlm.nih.gov

Lung stereotactic body radiation therapy (SBRT) delivered over 4 or 11 days: a comparison of acute toxicity and quality of life - PubMed

Grade 2 or higher acute toxicity was more common in the 4 day group, approaching statistical significance. More patients treated on 4 consecutive days reported a clinically meaningful increase in dyspnea, although interpretation of these results is challenging due to baseline imbalance between...

pubmed.ncbi.nlm.nih.gov

Whether any of the lung SBRT data extrapolates to spine SBRT is TBD.

 

[scarbrtj]

The QD vs QOD thing is a thing. I was surprised at that Green Journal reference when it came out. There's been data the other way too (well, no difference seen) as mentioned. IMHO, do what you want on schedule. No hard data the QOD is *worse* that's for sure.