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The aim of this presentation if to provide the audience with the approach developed at the Sunnybrook Health Sciences Center specific to MR-Linac adaptive radiotherapy for brain tumours. Our program initially treated with an adapt-to-position strategy and developed advanced research imaging capacity on the MR-Linac itself. As our workflow and understanding of the technology matured, we began the first trial of adaptive margin reduced radiotherapy for high grade glioma. The UNITED (UNIty-Based MR-Linac Guided AdapTive RadiothErapy for High GraDe Glioma: A phase 2 Trial, NCT04726397) trial is the first of its kind with a 5 mm personalized clinical target volume, that can be adjusted to take involved FLAIR, with weekly on-line adaption during either a patient’s 3 or 6 week course of radiotherapy concurrent with temozolomide. The UNITED trial is nearly complete with a target accrual of ~100 patients. The next phase of glioma adaptive trials has already begun at the Sunnybrook Health Sciences Center. We have learned much as to the technical challenges and opportunities. Our aim ultimately is to apply MRI-based quantitative metrics to identify areas to dose escalate or de-escalate during a patient’s treatment course. We are excited to share with you this unique experience to advance and modernize radiotherapy for this challenging disease.