Background
Consensus guidelines from the International Spine Radiosurgery Consortium (ISRC). Systematic review and consensus process involving 10 expert radiation oncology institutions with extensive SBRT experience. Addressed key technical and clinical questions for spinal SBRT: target volume delineation (GTV, CTV, PTV), dose/fractionation, critical structure constraints (spinal cord, cauda equina, nerve roots), and quality assurance requirements.
Interventions and follow up
Arm A: N/A — expert consensus/guideline document
Primary endpoint: Consensus recommendations on target volume and dose
mFollow up: N/A
Primary endpoint: Consensus recommendations on target volume and dose
mFollow up: N/A
Results
Key technical recommendations: GTV = gross disease; CTV = GTV + involved bone compartment; PTV = CTV + 2 mm (institutional)
Dose recommendations: 24 Gy/1 fx (de novo), 18–20 Gy/1 fx (re-irradiation); 24–27 Gy/2–3 fx; 30 Gy/5 fx
Spinal cord constraint: Dmax ≤14 Gy/1 fx; Dmax ≤20 Gy/2 fx; Dmax ≤23 Gy/3 fx
GTV-to-CTV expansion: Entire involved vertebral segment recommended for bone marrow disease
Dose recommendations: 24 Gy/1 fx (de novo), 18–20 Gy/1 fx (re-irradiation); 24–27 Gy/2–3 fx; 30 Gy/5 fx
Spinal cord constraint: Dmax ≤14 Gy/1 fx; Dmax ≤20 Gy/2 fx; Dmax ≤23 Gy/3 fx
GTV-to-CTV expansion: Entire involved vertebral segment recommended for bone marrow disease
Adverse events
Main adverse events: Radiation myelopathy risk: <1% when cord constraints respected. Vertebral compression fracture: 10–40% depending on lesion characteristics and dose. Esophageal toxicity and nerve root pain are key concerns for thoracic and lumbar spine SBRT.
Conclusions
ISRC consensus guidelines provide standardized target volume delineation and dose constraints for spinal SBRT that have been widely adopted across institutions. Adherence to cord dose constraints (Dmax ≤14 Gy single fraction) minimizes radiation myelopathy risk to <1%.
Key Limitations
Key Limitations: Expert consensus; level of evidence is III. Dose recommendations are not based on randomized trial data. Institutional variation in treatment planning systems and immobilization affects PTV margin recommendations. Re-irradiation cord tolerance constraints are less well-validated.
Clinical Context
ISRC guidelines (Cox BW et al, IJROBP 2012) are the standard reference for spinal SBRT target volume delineation worldwide. They are incorporated into AO Spine recommendations, ASTRO guidelines, and most academic spine SBRT programs. Image-guidance (CBCT, ExacTrac, intrafraction monitoring) is mandated.
References