Results of a Randomized Phase 2 Trial of One Versus Two 8 Gy Fractions for Painful Bone Metastases.

contextSingle-fraction 8 Gy palliative radiotherapy (RT) is a standard regimen for the relief of painful bone metastases. However, the delivery of single-fraction RT may result in higher retreatment rates compared to longer courses.

objectivesTo compare 6‑month retreatment rates after 8 Gy x 1 versus 8 Gy x 2 and evaluate pain response, quality of life, and adverse events (AEs).

methodsIn this prospective, randomized, multi-center phase 2 trial, adults with painful bone metastases were randomized to 8 Gy x 1 (arm 1) or 8 Gy x 2 (arm 2). The primary endpoint was the 6-month cumulative incidence of retreatment, with death as a competing risk. Secondary endpoints included pain response, adverse events, and quality of life using multiple patient-reported outcome measures.

resultsA total of 102 patients were randomized and treated (51 per arm). The 6-month retreatment rates were 11.5% in arm 1 v. 10.3% in arm 2 (p = 1.00). The cause-specific hazard ratio of retreatment in arm 2 (v. arm 1) was 0.87 (p = .83). Rates of death without retreatment at 6-months were 23.3% and 29.4%, respectively. Pain response rates at 3 months were similar between arms: 55% v. 72% in arms 1 v. 2, respectively (p = .20). No substantial differences in QOL were observed between groups. Grade 2+ AEs occurred in 13.7% and 15.7% (p = .78).

conclusionNo differences were observed in retreatment rates, pain response, or QOL between 8 Gy x 1 and 8 Gy x 2. Single-fraction palliative RT remains a standard for patients with painful bone metastases.