1. Pediatric oncology Emma Children's Hospital Amsterdam UMC Vrije Universiteit Amsterdam Amsterdam the Netherlands
2. Princess Máxima Center for Pediatric Oncology Utrecht the Netherlands
3. Department of Epidemiology and Biostatistics Amsterdam UMC Vrije Universiteit Amsterdam Amsterdam the Netherlands
4. Department of Pediatric Oncology Erasmus Medical Center Rotterdam/Sophia Children's Hospital Rotterdam the Netherlands
5. Department of Pediatric Hemato‐Oncology University Hospitals Leuven and Catholic University Leuven Leuven Belgium
6. Department of Pediatrics Clinique du MontLégia The Centre Hospitalier Chrétien Liège Belgium
7. Department of Pediatric Onco‐Hematology Universitair Ziekenhuis Brussel Brussels Belgium
8. Department of Paediatric Haematology‐Oncology and Stem Cell Transplantation Ghent University Hospital Ghent Belgium