Background
Phase II/III RCT (RTOG 0631). 339 patients with 1–3 spinal metastases and pain or neurologic symptoms. Compared single-fraction spinal SBRT (16–18 Gy) vs conventional fractionated RT (8 Gy/1 or 30 Gy/10). Phase II aimed to demonstrate feasibility; phase III compared pain response. Oligometastatic spine disease with high-performance status patients eligible. Evaluated whether SBRT provides superior pain control vs conventional RT for spinal metastasis.
Interventions and follow up
Arm A: Spinal SBRT: 16 Gy (epidural disease) or 18 Gy (no epidural) × 1 fraction to spine lesio
Arm B: Conventional RT: 8 Gy × 1 fraction (single fraction arm)
Primary endpoint: Pain response at 3 months (≥3-point reduction on NRS-11)
mFollow up: 3 months (primary); 2 years (secondary)
Arm B: Conventional RT: 8 Gy × 1 fraction (single fraction arm)
Primary endpoint: Pain response at 3 months (≥3-point reduction on NRS-11)
mFollow up: 3 months (primary); 2 years (secondary)
Results
Pain response (SBRT): 40.3% vs conventional 27.8%, P=.06 — not statistically significant
Local control (SBRT at 1 yr): 84% vs conventional 57%, P<.001
Grade ≥3 pain flare: 6.9% (SBRT) vs 1.9% (conventional)
Local control (SBRT at 1 yr): 84% vs conventional 57%, P<.001
Grade ≥3 pain flare: 6.9% (SBRT) vs 1.9% (conventional)
Adverse events
Main adverse events: SBRT: grade ≥3 pain flare 6.9%, higher than conventional (1.9%). Esophageal toxicity: grade ≥2 5% (SBRT). Radiation myelopathy: 0% in both arms. Vertebral compression fracture: 3.5% (SBRT) vs 1.9% (conventional).
Conclusions
SBRT achieved significantly superior local control compared to conventional single-fraction RT for spinal metastases but did not significantly improve pain response at 3 months (primary endpoint). The local control advantage supports SBRT for oligometastatic spine in patients where long-term tumor control is clinically relevant.
Key Limitations
Key Limitations: Pain response primary endpoint was not met (P=.06). Pain measurement is subjective. Three-month endpoint may be too early to capture the durability advantage of SBRT. Patients with prior spine RT were excluded. Epidural disease is a significant prognostic factor affecting both pain and local control.
Clinical Context
RTOG 0631 supports spinal SBRT for patients with limited spine metastases (particularly oligometastatic) where long-term local control is the priority. Conventional palliative RT (8 Gy × 1 or 20–30 Gy) remains standard for multiple symptomatic spine metastases with limited prognosis. SBRT is preferred for oligometastatic, previously irradiated, or radioresistant histologies (RCC, melanoma).
References