Background
Phase II/III RCT (RTOG 0631). 339 patients with 1–3 spinal metastases. Randomized to single-fraction spinal SBRT (16–18 Gy) vs conventional RT (8 Gy × 1). Evaluated pain response as primary endpoint in this palliative RT context. Full results published 2019. (Also referenced in Ch50 Oligometastatic Disease for local control context.)
Interventions and follow up
Arm A: Spinal SBRT: 16 Gy (epidural disease) or 18 Gy × 1 fraction to involved vertebral segment
Arm B: Conventional palliative RT: 8 Gy × 1 fractio
Primary endpoint: Pain response at 3 month
mFollow up: 24 month
Arm B: Conventional palliative RT: 8 Gy × 1 fractio
Primary endpoint: Pain response at 3 month
mFollow up: 24 month
Results
Pain response at 3 months (SBRT): 40.3% vs 8 Gy 27.8%, P=.06 — trend favoring SBRT (not significant)
1-yr local control (SBRT): 84% vs 8 Gy 57%, P<.001
Pain flare grade ≥3 (SBRT): 6.9% vs 8 Gy 1.9%
1-yr local control (SBRT): 84% vs 8 Gy 57%, P<.001
Pain flare grade ≥3 (SBRT): 6.9% vs 8 Gy 1.9%
Adverse events
Main adverse events: SBRT: grade ≥3 pain flare 6.9% — significantly higher than conventional. Esophageal toxicity grade ≥2: 5% (SBRT). No radiation myelopathy in either arm. Vertebral fracture: 3.5% (SBRT) vs 1.9% (conventional).
Conclusions
SBRT provided superior local control vs 8 Gy single fraction but did not significantly improve pain at 3 months — the primary endpoint was not met. For palliative intent in low-prognosis patients, conventional 8 Gy achieves equivalent pain palliation with less risk of pain flare. SBRT is preferred for oligometastatic, long-prognosis, or radioresistant disease.
Key Limitations
Key Limitations: Primary pain response endpoint not met (P=.06). Conventional arm was 8 Gy × 1 only — 30 Gy/10 is also standard and not compared. Pain measurement is subjective with limited sensitivity. Three-month pain endpoint may not capture SBRT durability benefit that emerges longer-term.
Clinical Context
RTOG 0631 guides clinical selection between SBRT and conventional RT for spine metastases. Conventional 8 Gy is preferred for symptomatic palliation in patients with poor prognosis and multiple bone metastases. SBRT is preferred for oligometastatic spine disease, prior irradiated sites, or radioresistant histologies (RCC, melanoma, sarcoma).
References