RT to brain tumours causes cognitive dysfunction. The extent of RT induced changes in cognitive function and radio-sensitivity of the brain is unknown. RT with protons instead of photons spares the healthy brain tissue more and is believed to reduce the risk of cognitive dysfunction. There is modest knowledge on which parts of the brain we need to spare, to prevent cognitive dysfunction.

The study is a prospective nationwide study including approximately 60 brain tumour patients from the four neuro oncology centres in Denmark. The patients will do patient reported outcome (PRO) and undergo neuropsychological assessment with standardized tests: They will do this prior to RT treatment and , 1, 3 and 5 years afterwards. The PRO's included measures on quality of life, fatigue, sleep, depression, anxiety, and socio demografica. The standardized tests are: Trail making Test (TMT); Hopkins Verbal Learning Test (HVLT); Controlled Oral Word Association Test (COWAT) - Animals and S; Coding and Digit Span from WAIS-IV; Paced Auditory Serial Addition Test (PASAT). The correlation between cognitive scores and RT dose-volume parameters to specific areas in the brain will be tested.

This study will elucidate the dose-response relationship in radiation-induced damage to substructures of the brain such as hippocampus, thalamus, temporal and frontal lobes that will allow the clinician to prioritize these structures in planning of proton radiotherapy.