Single vs. Multiple Fraction Trial of Stereotactic Ablative Radiotherapy for Comprehensive Treatment of Oligometastases/Progression

Inclusion Criteria: * 1-5 current oligometastatic or oligo-progressive lesions * Age 18 years or older * Able to provide informed consent * Able to complete electronic entry of patient reported outcomes and questionnaires independently or with assistance from a caregiver/family/friend/research staff using electronic methods after providing consent to email use. * Life expectancy \> 6 months * Histologically confirmed malignancy with metastatic disease detected on imaging. Biopsy of metastasis is preferred, but not required. * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Controlled primary tumor: defined as at least 3 months since original tumor treated radically, with no progression at primary site (can be considered controlled if no evidence of the primary tumour on imaging \[e.g. primary unknown\]) * A history and physical examination, including ECOG performance status, performed within 6 weeks prior to enrollment * Patient has had a CT chest, abdomen and pelvis or PET-CT within 10 weeks prior to enrollment, and within 13 weeks prior to treatment * Patient has had a nuclear bone scan (if no positron emission tomography-computed tomography \[PET-CT\]) within 10 weeks prior to enrollment, and within 13 weeks prior to treatment * Patient has had CT or MRI brain imaging if primary has a propensity for central nervous system metastases (if deemed appropriate by the treating investigator) within 10 weeks prior to enrollment, and within 13 weeks prior to tre…