1. Department of Pediatric Hematology and Oncology, Hannover Medical School, Hannover, Germany;
2. Pediatric Hematology and Oncology, Pediatrics III, University Hospital Essen, Essen, Germany;
3. Dutch Childhood Oncology Group, Den Haag, The Netherlands;
4. Department of Immunology, Laboratory Medical Immunology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands;
5. Department of Pediatric Psychiatry and Psychosomatic Medicine, Landschaftsverband-Rheinland Clinic, University Duisburg/Essen, Essen, Germany;
6. Department of Pediatric Oncology/Hematology, Erasmus Medical Center/Sophia Children's Hospital, Rotterdam, The Netherlands; and
7. Department of Pediatric Hematology and Oncology, Martin Luther University Halle-Wittenberg, Halle, Germany