Do you use a comprehensive volumetric, rather than numeric, cutoff in consideration of SRS vs WBRT for brain metastases?  

If a patient has a limited number of brain metastases (e.g., < 3 total) but the additive volume of these intracranial metastases is high (e.g., each lesion is 100 cc to 125 cc's, such that the total volume is ~400 cc's) do you employ selectively employ WBRT versus SRS?

If so, what is the total volume of intracranial metastatic disease that serves as a cutoff between SRS vs WBRT approaches to palliation?