Mets Near Sagittal Sinus

[Mandelin Rain]

Does anyone modify SRS dose for mets near the sagittal sinus?

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[Gfunk6]

No. Since vascular ablation after SRS is a relatively slow processes, collaterals can develop.

 

[Reaganite]

My neurosurgeons will often ask me to do FSRT for lesions near the sagittal sinus, and they are normally extremely aggressive with single fraction SRS. I think the issue is more related to an increased risk of peritumoral edema with parasagittal lesions treated with single fraction srs.

 

[Cancerdancer]

There are numerous reports of significantly higher rates of peritumoral edema after SRS for parasagittal meningiomas...I'm sure that's where their caution is coming from, and rightfully so. Reason for that observation isn't clear...for meningiomas it's really a "basal" vs "non-basal" observation. Assumption is that more interface with the pial surface, with vascular/venous occlusion also a potential factor near the sinus. Leland Rogers I believe has summarized this in some meningioma reviews.
How that should impact dose, and whether pertinent for mets...unclear to my knowledge. If it's small met without contact of the dura I wouldn't worry too much just about the sagittal sinus getting dose...but if it's 3.5 cm superficial location you might wanna fractionate or modify dose accordingly.

 

[seper]

Agree with decreasing dose relative to RTOG cookbook, that's a kind of accepted standard practice for meningiomas for reasons outlined above.

 

[Gfunk6]

Is there any data to support the statements above? Could not find any in the Red Journal.

 

[radiaterMike]

Is there any data to support the statements above? Could not find any in the Red Journal.

Don't think so. The reasons menigiomas have greater risk of edema may not be relevant brain metastases. I would not treat parasagittal brain metastases differently. A symptomatic toxicity can be surgically salvaged as can a recurrence but I think recurrence is more likely if you skimp too much on dose. For meningioma in parasagittal location I consider 3-5 fraction although don't have data to strongly support it being less risky.

 

[seper]

http://www.ncbi.nlm.nih.gov/pubmed/18812954

 

[BobbyHeenan]

There was also an abstract presented from the 2013 Radiosurgery Society meeting outlining increased seizure risk for parasaggital meningiomas - see page 23 on the link below.

http://therss.org/UploadedDocs/2013 SRS SBRT Mtg/Abstract bookFINALforweb.pdf