APPROACH: Analysis of Proton versus Photon Radiotherapy in Oligodendroglioma and Assessment of Cognitive Health - study protocol paper for a phase III multicentre, open-label randomised controlled trial.

Introduction: Oligodendroglioma (ODG) is a rare type of brain tumour, typically diagnosed in younger adults and associated with prolonged survival following treatment. The current standard of care is maximal safe debulking surgery, radiotherapy (RT) and adjuvant procarbazine, lomustine and vincristine (PCV) chemotherapy. Patients may experience long-term treatment-related toxicities, with RT linked to impairments of neurocognitive function (NCF) and health-related quality of life (HRQoL).