Spine SABR - Dose-escalated Stereotactic Ablative Body Radiotherapy (SABR) for Solid Tumour Spine Metastases

Inclusion Criteria: 1. Written informed consent obtained prior to any study-related procedures 2. ≥ 18 years of age 3. Life expectancy \> 6 months 4. ECOG (Eastern Cooperative Oncology Group) performance status (PS) 0-2 5. Histological diagnosis of malignant primary disease (excluding haematologic, seminomatous or small cell subtype) 6. Diagnosis of oligometastatic disease (OMD) or oligoprogressive disease (OPD) defined as: 1. OMD where there are 1 to 5 metastatic lesions, with a controlled primary tumor being optional, but where all metastatic sites must be safely treatable (can be synchronous or metachronous to primary tumor diagnosis) with curative intent OR 2. OPD with 1 to 5 lesions progressing on a background of widespread but stable metastatic disease OR 3. Systemic therapy-induced OMD where there are 1 to 5 persistent lesions after systemic therapy, all safely treatable with SABR 7. Single spinal level from C1 to L5 to be treated for the purpose of the study (co-existing lesion(s) on non-consecutive spinal level(s) may receive RT at Investigator discretion, if deemed unlikely to interfere with study treatment and assessment of outcomes). 8. Stable spine assessed by Spinal Instability Neoplastic Score (SINS) (SINS 0-6, or SINS 7-12 and not for surgical intervention). 9. Bilsky Grade 0-1a (i.e. minimal (epidural impingement, without deformation of thecal sac) or no epidural disease) as confirmed by Radiation Oncologist 10. Able to lie flat in the treatment position for radiotherapy for up to 60 minutes 11. Females of childbearing potential must not be pregnant or lactating, and must be prepared to take adequate contraception methods during treatment. Males whose female partners are of childbearing potential must be prepared to take adequate contraception methods during treatment. Examples of effective contraception methods are a condom or a diaphragm with spermicidal jelly, or oral, injectable or implanted birth control Exclusion Criteria: 1. Previous radiotherapy or surgery to the proposed SABR treatment site which is likely to interfere with treatment or assessment of outcomes (for radiotherapy, this includes prior thoracic radiotherapy to the lung or oesophagus which would result in overlap of fields if a T spine lesion will be treated) 2. Patients with symptomatic spinal cord compression or cauda equina syndrome, resulting in bony compression or epidural compression of the spinal cord or cauda equine, respectively 3. Patients with syndromes or conditions associated with increased radiosensitivity 4. Patients with radiosensitive histologies, e.g. myeloma or lymphoma 5. Contraindication to MRI, e.g. MRI-incompatible personal pacemaker in situ 6. Patients with pre-existing osteoporotic fractures of the spine 7. Prior treatment with any radionuclide within 30 days prior to registration 8. Patients who have received chemotherapy within 1 week prior to administration of protocol RT or who are expected/planned to receive chemotherapy during RT or within 1 week after completing protocol RT 9. Uncontrolled intercurrent illness that is likely to interfere with treatment or assessment of outcomes, or psychiatric illness/social situations that would limit compliance with study requirements 10. Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the study, or if it is felt by the research / medical team that the patient may not be able to comply with the protocol and follow-up schedule due to psychological, familial, sociological or geographical conditions 11. Significant or progressive neurological deficit such that emergency surgery or radiation required