Single- vs. Two-Fraction Spine Stereotactic Radiosurgery for the Treatment of Vertebral Metastases

The primary objective of this study is to establish the non-inferiority in vertebral compression fracture (VCF) incidence at 6 months between single-fraction and two-fraction sSRS.

Other objectives are to to evaluate the 12-month impact of single- and two-fraction sSRS on local control (LC), pain control (PC), quality of life (QOL), and toxicity (specifically, pain flare, radiation esophagitis/laryngitis/pharyngitis, and radiation myelitis)

This study is planned as a two-arm randomized phase II trial to establish non-inferiority of single fraction sSRS compared to two-fraction sSRS. Approximately 130 participants will be enrolled in this trial; 65 participants in each arm:

• Group 1: If you are assigned to this group, you will undergo spine radiosurgery in a single (1) session.
• Group 2: If you are assigned to this group, you will undergo spine radiosurgery in two (2) sessions.

Inclusion criteria

• Karnofsky Performance Status (KPS) ≥ 70
• RPA class 1 (KPS >70 AND controlled systemic disease) or RPA Class 2 (KPS >70, uncontrolled systemic disease OR KPS ≤70, age ≥54, no visceral metastases)44 (see Appendix II)
• Vertebral metastases from C3 to L5 based on bone scan, CT, PET, or MRI.
• Vertebral metastases must be (1) solitary, (2) at two contiguous levels, or (3) a maximum of three separate sites, with a maximum of two contiguous levels.
• Radioresistant metastases are permitted (including sarcomas, melanomas, and renal cell carcinomas).
• Patients with epidural disease are permitted so long as there is no cord compression.
• Paraspinal extension is permitted, so long as the paraspinal component is ≤5 cm
• Multiple small metastatic lesions (<20% vertebral body involvement) of no clinical correlate are permitted, and not included in the irradiated segments as per RTOG 0631
• History and physical within four weeks of registration.
• Negative pregnancy test within four weeks of registration for women of childbearing potential.
• Diagnostic spine MRI with and without contrast within four weeks of registration
• Neurological exam within four weeks of registration to rule out rapid neurological decline. Mild to moderate neurological deficits are acceptable, as long as distance between lesion and spinal cord is ≥3 mm
• Patients may have prior EBRT at the index site.
• Informed consent of the participant.

Exclusion criteria

• Lesions at C1-2 or S1-Coccyx.
• Hematologic malignancies including lymphoma and myeloma.
• Multiple primary cancers.
• Primary neoplasms of the spine
• Prior corpectomy, kyphoplasty/vertebroplasty, or instrumentation at the site of planned sSRS.
• Spinal cord compression.
• Paraspinal mass >5 cm.
• Patients with rapid neurologic decline.
• Bony retropulsion resulting in neurologic deficit.
• Patients with contraindications to MRI.
• Patients allergic to intravenous contrast for MRI or CT.
• Patients with emergent spinal cord compression.
• Patients with mechanical instability of the spine.
• Patients with active connective tissue disease.
• Patients who previously underwent sSRS to the vertebrae of interest.
• Patients with diffuse or multilevel metastatic spinal disease with >20% involvement of vertebral bodies, defined as involvement of >5 vertebral levels.
• Inability to participate in study activities due to physical or mental limitations.
• Inability or unwillingness to return for all required follow-up visits and imaging.
• Inability to deliver sSRS, either 18 Gy in one fraction, or 24 Gy in two fractions.