affiliation not provided to SSRN, Leiden University - Leiden University Medical Center (LUMC), Leiden University - Department of Medical Statistics, Erasmus MC - Brain Tumor Centre, Netherlands Cancer Institute - Division of Psychosocial Research and Epidemiology, affiliation not provided to SSRN, affiliation not provided to SSRN, KU Leuven, European Organisation for Research and Treatment of Cancer (EORTC), EORTC Headquarters, University of Bonn - University Hospital Bonn (UKB), University Hospital Zurich, affiliation not provided to SSRN, Université de Lille - Laboratoire Protéomique, affiliation not provided to SSRN, affiliation not provided to SSRN, Medical University of Vienna, affiliation not provided to SSRN, affiliation not provided to SSRN, International BrainTumour Alliance, IRCCS Regina Elena National Cancer Institute, affiliation not provided to SSRN, University of Amsterdam - Amsterdam University Medical Centers, affiliation not provided to SSRN, University Hospital Zurich, Universitätsklinikum Leipzig, University of Lausanne, Heidelberg University - University Hospital Heidelberg, University Hospital Zurich, Leiden University - Leiden University Medical Center (LUMC) and affiliation not provided to SSRN