1. Department of Pediatrics and Pediatric Hematology/Oncology, University Children's Hospital, Carl von Ossietzky University , Klinikum Oldenburg AöR, Oldenburg 26133 , Germany
2. Department of Pediatric Hematology/Oncology, University of Bonn Medical Center , Bonn , Germany
3. Diagnostic and Interventional Neuroradiology, Faculty of Medicine, Department of Neuroradiology, University Hospital of Augsburg , Augsburg , Germany
4. Institute of Biostatistics and Clinical Research, University of Münster , Münster , Germany
5. Department of Particle Therapy, University Hospital Essen , Essen , Germany
6. Department of Neurosurgery, University Medical Center Hamburg-Eppendorf (UKE) , Hamburg , Germany