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

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 (seeAppendix 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) amaximum of three separate sites, with a maximum of two contiguous levels.

• Radioresistant metastases are permitted (including sarcomas, melanomas, and renalcell carcinomas).

• Patients with epidural disease are permitted so long as there is no cordcompression.

• Paraspinal extension is permitted, so long as the paraspinal component is ≤5 cm

• Multiple small metastatic lesions (<20% vertebral body involvement) of no clinicalcorrelate 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 childbearingpotential.

• Diagnostic spine MRI with and without contrast within four weeks of registration

• Neurological exam within four weeks of registration to rule out rapid neurologicaldecline. Mild to moderate neurological deficits are acceptable, as long as distancebetween 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 ofplanned 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% involvementof 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.