What is the appropriate target volume for SBRT to a non-vertebral osseous metastasis?

For non spine bone metastases, I usually treat the GTV with a 1 cm expansion of continguous bone to CTV + 0.3-0.5 cm margin in all dimensions to PTV. With this amount of contiguous bone, I will usually treat the entire circumference of the long bone. I rarely treat GTV + a small PTV expansion as ane...