How do you decide on a fractionation scheme for retreatment of a progressive/painful spine metastasis?

The NCIC CTG SC20 trial tested retreatment of bone metastases and included patients with spine metastases. Both 8 Gy in 1 fraction and 20 Gy in multiple fractions for retreatment were found to be effective and safe, with a low risk of serious adverse events. The minimum time interval between initial...