1. Department of Pediatric and Adolescent Oncology, Institute Gustave Roussy, 114 rue Edouard Vaillant, 94805 Villejuif, France
2. Department of Oncology, Alder Hey Children's NHS Foundation Trust, Liverpool, UK
3. Department of Pediatric Hematology/Oncology, CHU Amiens, Amiens, France
4. Biostatistics and Epidemiology Unit, Institute Gustave Roussy, Villejuif, France
5. Department of Radiology, Institute Gustave Roussy, Villejuif, France