Hypofractionated stereotactic RT for brain mets

[Palex80]

Hi!

I'd like to hear your opinions on fractionation schedules and treatment techniques in hypofractionated stereotactic RT for brain mets. I am not talking about radiosurgery, but rather treatments with 3-6 fractions with the goal of tumor ablation in mind. I am also talking abour primary, not postoperative treatments.

What do you usually prescribe?
3x7Gy, 4x6Gy, 5x5Gy, 5x6Gy, 6x5Gy, 6x6Gy...

And do you prescribe the dose usually to the 100% isodose around the PTV or do you do some kind of radiosurgery-like technique (80% isodose, etc.)?

We usually give 5x6Gy and prescribe the dose to the 100% isodose around the PTV, with the PTV being GTV+3mm. However I've seen a couple of local failures, so I am thinking of taking it higher to 6x6Gy.

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[medgator]

What is the rationale for doing that instead of single-Fx? Larger mets?

 

[Palex80]

Yes, larger mets as well as sometimes concerns in patients who have already been heavily treated before with radiosurgery + WBRT for other mets in the vicinity.

 

[Gfunk6]

I do 5 Gy x 5 fractions prescribed to the 80% isodose line.

 

[OTN]

There's good data (can't remember from where but have the paper somewhere) suggesting 9 Gy x 3 to the tumor bed s/p resection leads to good rates of control with a relatively low chance of radionecrosis, so I do that for all brain mets larger than 4 cm. I Rx to the PTV, which I do expand 1mm from the GTV. I've had good results with this regimen (knock on wood) thus far.

 

[medgator]

There's good data (can't remember from where but have the paper somewhere) suggesting 9 Gy x 3 to the tumor bed s/p resection leads to good rates of control with a relatively low chance of radionecrosis, so I do that for all brain mets larger than 4 cm. I Rx to the PTV, which I do expand 1mm from the GTV. I've had good results with this regimen (knock on wood) thus far.

I guess post-op WBRT has fallen by the wayside...

 

[OTN]

I guess post-op WBRT has fallen by the wayside...

I try and do whole brain RT only when necessary, and the data is starting to support that approach very well. People just don't do very well following whole brain RT. When I do treat with whole brain, I always try and do hippocampal-sparing whole brain as per RTOG 0033, as long as the patient has well-controlled extracranial disease.

 

[Mr RADical]

I try and do whole brain RT only when necessary, and the data is starting to support that approach very well. People just don't do very well following whole brain RT. When I do treat with whole brain, I always try and do hippocampal-sparing whole brain as per RTOG 0033, as long as the patient has well-controlled extracranial disease.

This is certainly the case at our institution. Whole brain tends to be looked at as a last resort.

 

[seper]

Regarding postop SRS to resection cavity: does anyone work at a place that does it with Gamma Knife?

 

[medgator]

This is certainly the case at our institution. Whole brain tends to be looked at as a last resort.

Are you guys sticking to the the standard 3-4 lesions max for SRS when considering deferring/avoiding WBRT or are you being more liberal with that?

 

[Palex80]

I stick to 3.

I also don't like doing SRS for poorly differentiated non-SCC of the lung. They tend to relapse with numerous lesions usually.

 

[Mr RADical]

We do not use 3-4 lesions as a cutoff. We tend to base it on a patient to patient basis and heavily weigh their prognosis and performance level. Not infrequently we will treat more than 4 lesions in a patient.

 

[medgator]

I stick to 3.

I also don't like doing SRS for poorly differentiated non-SCC of the lung. They tend to relapse with numerous lesions usually.

I agree. They didn't study pci in nsclc for nothing even if it didn't quite pan out

 

[medgator]

We do not use 3-4 lesions as a cutoff. We tend to base it on a patient to patient basis and heavily weigh their prognosis and performance level. Not infrequently we will treat more than 4 lesions in a patient.

I think outside of certain academic centers, you won't find that to be the norm

 

[Palex80]

One Dutch center has shown preliminary results of a WBRT-schedule with 5x4Gy with hippocampal sparing and integrated VMAT/RapidArc boost to the GTVs to 5x8Gy for multiple brain mets.
Perhaps this may be somehow the way to go. If you are treating numerous wildly dispersed metastases you eventually get overlapping exposures from your numerous SRS leading more or less to >50% of the brain getting a low dose "bath".
Perhaps if you integrate it all into a one series schedule with integrated boosts you will get the same result.

One point to be made is of course $$$:
I am not certain how this is in the US. Are you allowed to charge for every single SRS procedure? So if you are doing 5 mets, would you be able to charge 5x the fee of a single SRS?
In certain European countries this is regulated, you are not allowed to charge for more than a certain number of SRS within a certain time span for the same patient.

 

[medgator]

One point to be made is of course $$$:
I am not certain how this is in the US. Are you allowed to charge for every single SRS procedure? So if you are doing 5 mets, would you be able to charge 5x the fee of a single SRS?
In certain European countries this is regulated, you are not allowed to charge for more than a certain number of SRS within a certain time span for the same patient.

I believe that used to be the case here. Now you can't push more than one code per day, so I have heard that certain unscrupulous places will bring patients back on different days for different lesions (kinda like in dermatology).