A randomized trial of single versus multiple fractions (Fx) for re-irradiation (RE-RT) of painful bone metastases (PBM): NCIC CTG SC.20.

9502 Background: The optimal RE-RT dose and fractionation schedule for PBM is uncertain. Methods: Patients (pts) with PBM after previous radiation (RT) to the same site were stratified by previous Fx schedule and pain response and randomized to 8 Gy in 1 Fx or 20 Gy in 5 Fx (8 Fx if previous RT was to spine/whole pelvis in multiple Fx). The primary endpoint was overall response rate (RR) at 2 months using the International Consensus schema (Chow 2002) which combines Brief Pain Inventory worst pain score and opioid analgesic use. We tested if 8Gy was non-inferior (NI), analyzed by intention to treat (ITT) and a per-protocol (PP) sensitivity analysis excluding those who were ineligible, inevaluable or received non-allocated therapy. Sample size was calculated using an expected RR of 70% with 20Gy and a NI margin of 10% (i.e. upper boundary of 1-sided 95% CI for the RR difference). Pts reported adverse events (AEs) by questionnaire on Day 14. Quality of life (QoL) was assessed using the EORTC QLQ C30. Result...