FSRT for Cavernous SInus Meningioma

[Gfunk6]

89F with ~3.5 cm R cavernous meningioma (Grade I). She has multiple co-morbidities and is unresectable. Since she's asymptomatic, we have been following her with semi-annual MRIs. However, it has recently encroached into the prepontine cistern and the tumor board recommendation is to treat.

Normally, I'd do 1.8 Gy to 45-50.4. However, I'd like to spare her the five weeks of treatment if possible so I was thinking about fractionated stereotactic radiosurgery. Data is sparse, but here are some BED calcs I came up with:

With an alpha/beta of 3 and 14 Gy x 1, BED(3.0) is 79.33

5 Gy x 5, BED(3.0) is 66.67.

5.5 Gy x 5, BED(3.0) is 77.92.

1.8 Gy x 25, BED(3.0) is 72.00.

Based on these calcs, I was considering 5.5 Gy x 5. But then the question is, what should the brainstem point dose max be?

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[deleted4401]

I think great care must be taken with utilizing simple radiobiologic models to compare SRT with EBRT. A lot of things have to be considered, including the time of delivery (5 weeks vs however many weeks you're doing it in). I don't think 5.5 x 5 Fx is bad or unsafe. I just think you can't really even somewhat accurately compare it with EBRT using (d)(fx)*(1+d/3.0). I think safer to just get in touch with the Stanford or UPMC guys and see what they do, and just copy that.
S

 

[medgator]

I think great care must be taken with utilizing simple radiobiologic models to compare SRT with EBRT. A lot of things have to be considered, including the time of delivery (5 weeks vs however many weeks you're doing it in). I don't think 5.5 x 5 Fx is bad or unsafe. I just think you can't really even somewhat accurately compare it with EBRT using (d)(fx)*(1+d/3.0). I think safer to just get in touch with the Stanford or UPMC guys and see what they do, and just copy that.
S

Agreed. BED calcs are notoriously difficult for srs/sbrt and the conventional equations just don't cut it, a point that's made often during sbrt lectures. I'd seek out some advice.

Seminars did have an article on sbrt tolerances a couple years back

http://www.semradonc.com/article/S1053-4296(08)00030-1/fulltext

 

[BraggPeak]

I would definitely stick with 54/1.8 Gy. I wouldn't play with dose-fractionation, especially in the cavernous sinus, outside of a clinical trial protocol....unless you know a good lawyer!

 

[BraggPeak]

Not sure what other people are using, be we never go to 45 Gy for meningiomas. We sometimes cut down to 52.2 Gy or 50.4 Gy if it is an optic nerve sheath meningioma.

 

[deleted4401]

50.4 for type 1, 54 for type 2, 59.4 for type 3 is what I learned.

I don't think it's off the reservation or inviting litigation to do FSRT for cavernous sinus meningiomas. Its just I wouldn't want to be the guy calculating the dose to give. You have plenty of cover with poor outcomes with EBRT and reasonably good outcomes with GK. If the patient was sent to me, I'd send them to a place that does SRS/FSRT, rather than give them 50-54 Gy with IMRT

 

[BraggPeak]

We do FSRT with conformal dynamic arcs (usually 6) to 54 Gy and in cases where we can't meet dose constraints, FSRT using IMRT to 54 Gy.

 

[Palex80]

5 x 5 (or even 5.5 Gy probably) is doable.
You can also consider 10 x 3.5 Gy (it has been done before for GBM).

Anyways, since she's 89 years old and has several comorbidities, you probably need to control the tumor for only a couple of years, right?

 

[Reaganite]

89F with ~3.5 cm R cavernous meningioma (Grade I). She has multiple co-morbidities and is unresectable. Since she's asymptomatic, we have been following her with semi-annual MRIs. However, it has recently encroached into the prepontine cistern and the tumor board recommendation is to treat.

Normally, I'd do 1.8 Gy to 45-50.4. However, I'd like to spare her the five weeks of treatment if possible so I was thinking about fractionated stereotactic radiosurgery. Data is sparse, but here are some BED calcs I came up with:

With an alpha/beta of 3 and 14 Gy x 1, BED(3.0) is 79.33

5 Gy x 5, BED(3.0) is 66.67.

5.5 Gy x 5, BED(3.0) is 77.92.

1.8 Gy x 25, BED(3.0) is 72.00.

Based on these calcs, I was considering 5.5 Gy x 5. But then the question is, what should the brainstem point dose max be?

Towards the tail end of my training, my institution seemed to be transitioning mostly to these 5-fraction regimens. I recently treated several 3cm-ish meningiomas and acoustic neuromas with a 5 x 5 regimen and the patients did well. I believe there is some data out of stanford on this approach. I have also read about 3 Gy x 10. We used the Timmerman paper for our dose constraints: http://www.ncbi.nlm.nih.gov/pubmed/18725106

 

[medgator]

. I have also read about 3 Gy x 10.

A palliative regimen?

 

[deleted4401]

If you're going to do 3 Gy x 10, couldn't you just do lateral fields?

 

[Gfunk6]

Thanks everyone for the input.

A couple of follow-up questions:

1. Is there any published data for a 5 x 5 Gy data for meningiomas?

2. When you say FSRT to a total dose of ~50.4 Gy, what is the point of using stereotaxis? You are nowhere near brainstem or optic tolerance. You could instead use a nice multi-field 3D conformal plan with weekly ports. I understand using daily CBCT for high grade malignancies with nearby avoidance structures but why in this case?

 

[deleted4401]

Doesn't Randy Waggoner have a series?

 

[BraggPeak]

We do FSRT to 54 Gy. We contour the lesion on a fused MRI and have no margin (not even for penumbra).

Simul, when you say you do 50.4 Gy for Type I, most people don't biopsy base of skull meningiomas, so you dont really know if its type I vs atypical, right (although it's almost always type I)?

 

[deleted4401]

Sorry, I didn't mean to say I actually do it. I'd send 'em for radiosurgery. Unless it looks aggressive/invasive (bone changes, necrosis, etc.), I think we are to presume if they are localized they are grade 1 and tx without biopsy, and then if it progresses than we can retrospectively assume it was higher grade?
S

 

[Gfunk6]

Towards the tail end of my training, my institution seemed to be transitioning mostly to these 5-fraction regimens. I recently treated several 3cm-ish meningiomas and acoustic neuromas with a 5 x 5 regimen and the patients did well. I believe there is some data out of stanford on this approach. I have also read about 3 Gy x 10. We used the Timmerman paper for our dose constraints: http://www.ncbi.nlm.nih.gov/pubmed/18725106

That paper was awesome, especially Table 2. Thanks for the link!

The title of Table 2 is both humorous and scary at the same time: "Mostly unvalidated normal tissue dose constraints for SBRT"

 

[Palex80]

We do FSRT to 54 Gy. We contour the lesion on a fused MRI and have no margin (not even for penumbra).

I find this kind of troubling.
I guess it depends a lot on what you consider "GTV" on MRI. I've always had lots of trouble deciding what is GTV and what is not in skull base meningeomas, due to their proximity to vessels. That's why we usually give a 5mm CTV margin for Grade I meningeomas (excluding brain, bones, etc) and then another 3 mm margin for the PTV.
Presumably it has a lot to do with the techniques we use. 54 Gy are good to control macroscopic tumor, but even with the most conformal techniques the 80-90% isodoses are bound to extend up to 1 cm or more beyond your GTV anyways, so I guess those 80-90% of dose are good enough to kill off microscopic meningeomas deposits.
If you use protons on the other hand,you got yourself a whole different ball game.

 

[BraggPeak]

Our contours are done in conjunction with the neurosurgery department and a neuroradiologist is on-site if there are any questions. We prescribe the dose to an isodose line, so there may be more than our GTV that ends up getting 54 Gy.

 

[Reaganite]

I find this kind of troubling.
I guess it depends a lot on what you consider "GTV" on MRI. I've always had lots of trouble deciding what is GTV and what is not in skull base meningeomas, due to their proximity to vessels. That's why we usually give a 5mm CTV margin for Grade I meningeomas (excluding brain, bones, etc) and then another 3 mm margin for the PTV.
Presumably it has a lot to do with the techniques we use. 54 Gy are good to control macroscopic tumor, but even with the most conformal techniques the 80-90% isodoses are bound to extend up to 1 cm or more beyond your GTV anyways, so I guess those 80-90% of dose are good enough to kill off microscopic meningeomas deposits.
If you use protons on the other hand,you got yourself a whole different ball game.

Actually with protons and standard penumbra, set up, and range uncertainty margins, the 70-100% isodose lines are actually a little broader than you get with good xray plans. The sparing is really seen at the lower isodose levels. Not to fuel any controversy here , but if you look at standard opposed lateral proton prostate plans, for example, the rectal dvhs actually look slightly worse in the high dose areas compared to imrt plans.

 

[Palex80]

Actually with protons and standard penumbra, set up, and range uncertainty margins, the 70-100% isodose lines are actually a little broader than you get with good xray plans. The sparing is really seen at the lower isodose levels. Not to fuel any controversy here , but if you look at standard opposed lateral proton prostate plans, for example, the rectal dvhs actually look slightly worse in the high dose areas compared to imrt plans.

This is very dependent on the technique you use for protons (active scanning vs. scattering, spot size, number of fields used, etc) and applies to the dose that is delivered around the field you are using, not to the dose behind the Bragg peak.

I've worked in a proton facility before and it was standard there to give a "good" CTV margin to all meningeomas treated.

 

[Gfunk6]

Update: pt consented to fully fractionated XRT over 5.5 weeks.

Thanks to ACS volunteer drivers for making it possible!