What are the dose fractionation possibilities for Spinal Stereotactic Body Radiation Therapy (SBRT)?

From the Guidelines

Spinal SBRT typically employs dose fractionation schemes ranging from single-fraction to multi-fraction regimens, with common protocols including single-fraction doses of 16-24 Gy, three-fraction regimens of 8-10 Gy per fraction, and five-fraction regimens of 5-6 Gy per fraction. The choice between these options depends on several factors including tumor histology, prior radiation exposure, proximity to critical structures (especially the spinal cord), and the patient's overall condition 1. Single-fraction treatments offer convenience and may be preferred for patients with limited life expectancy or those who have difficulty with multiple visits, while multi-fraction regimens may provide better tumor control with potentially reduced toxicity to surrounding tissues.

Key Considerations

• Tumor histology: influences the choice of dose fractionation scheme
• Prior radiation exposure: affects the tolerance of surrounding tissues to additional radiation
• Proximity to critical structures: requires careful planning to avoid radiation myelopathy
• Patient's overall condition: influences the choice between single-fraction and multi-fraction regimens

Dose Fractionation Schemes

• Single-fraction doses: 16-24 Gy
• Three-fraction regimens: 8-10 Gy per fraction (total 24-30 Gy)
• Five-fraction regimens: 5-6 Gy per fraction (total 25-30 Gy)

Important Considerations for Treatment Planning

• Biological effective dose calculation: ensures adequate tumor coverage while respecting tolerance doses for the spinal cord and other organs at risk
• Planning target volume margin: typically 1-3 mm around the gross tumor volume
• Dose constraints: strict constraints to the spinal cord to prevent radiation myelopathy, as reported in studies such as 1 and 1.

From the Research

Dose Fractionation Possibilities for Spinal Stereotactic Body Radiation Therapy (SBRT)

• The dose fractionation possibilities for Spinal SBRT include:
  • 9-21 Gy in 1-3 fractions 2
  • 10-40 Gy in 1-5 fractions 3
  • 16-24 Gy in a single fraction, 24-30 Gy in two or three fractions, and 30-40 Gy in four or five fractions 4
  • 24 Gy in 2 daily fractions 5, 6
  • 28 Gy in 2 daily fractions 5
• These dose fractionation schemes have been used to treat various types of spinal tumors, including benign and malignant lesions, and have shown promising results in terms of local control and toxicity 2, 3, 4, 5, 6

Local Control and Toxicity Outcomes

• The local control rates for Spinal SBRT have been reported to be:
  • 76% at 5 years 2
  • 83.3% at 1 year for patients with prior RT, and 91.2% at 1 year for patients without prior RT 3
  • 83-93.9% at 1 year for 24 Gy in 2 fractions 6
  • 72-86% at 1 year for reirradiation of spine metastases that failed prior cEBRT 6
• The toxicity outcomes for Spinal SBRT have been reported to be:
  • No grade 3+ acute- or late-onset complication 2
  • No cases of Grade 4 toxicity, and rare cases of Grade 3 toxicity 3
  • Rates of plexopathy, radiculopathy, and myositis under 5%, with no cases of radiation myelopathy (RM) reported in the de novo setting when the spinal cord avoidance structure is limited to 17 Gy in 2 fractions 6