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 anecdotally, I have seen marginal recurrences from this type of treatment.

With respect to dosing, the largest literature on any bone metastasis is on spine SBRT and many institutions have extrapolated the doses from this type of treatment this to non spine bone metastases. I will consider treating with a single fraction to 16-24 Gy/1 fraction if there are no concerns for adjacent OARs or to 24-30 Gy/3 fractions. For the 3 fraction regimen, I will tr...