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

Treatment will consist of image guided dose escalated SABR using a simultaneous integrated boost (SIB) delivered in two fractions adhering to organ at risk dose-volume histogram constraints. There will be three dose levels delivered to the Planning Target Volume\_1 (PTV\_1) in each treatment arm as follows: 28 Gy (14 Gy per fraction), 30 Gy (15 Gy per fraction) and 32 Gy (16 Gy per fraction). A lower dose of 20 Gy (10 Gy per fraction) will be delivered to the PTV\_2 which will be defined according to international consensus guidelines (Cox et al., 2012). The dose to PTV\_2 will remain the same through all dose levels. All doses are prescribed to the target volume.