1. Department of Pediatric Oncology and Hematology, University of Cologne, Cologne, Germany
2. Division of Childhood Cancer Epidemiology, Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center, Mainz, Germany
3. Clinic of Pediatric Oncology and Hematology, University of Hamburg, Hamburg, Germany
4. Child and Adolescent Health, Pediatrics 5, Olgahospital, Stuttgart, Germany
5. Institute of Medical Statistics and Bioinformatics, University of Cologne, Cologne, Germany
6. Department of Pediatric Oncology Hematology Children’s Hospital, Cantonal Hospital, Luzern, Switzerland