Patients with a high grade glioma have an increasing overall survival and progression free survival after initial treatment. Because of a better performance status these patients are more often eligible for re-treatment with for example radiotherapy. However, to date only a few prospective studies on re-irradiation of gliomas exist and very little is known about the effects of re-irradiation on quality of life and cognition. This trial is designed to longitudinally establish the effects of re-irradiation on quality of life, cognition and physical performance in patients with a high grade glioma. Based on the currently available information the investigators hypothesize that quality of life after re-irradiation can be kept stable until further tumour progression.