1 Anne-Sophie Defachelles, MD, and Emilie Bogart, MD, Centre Oscar Lambret, Lille, France; Michela Casanova, MD, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy; Johannes H.M. Merks, MD, Princess Maxima Center for Pediatric Oncology, Utrecht, the Netherlands; Gianni Bisogno, MD, PhD, Department of Women and Children Health, University Hospital of Padova, Padova, Italy; Giuseppina Calareso, MD, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy; Soledad Gallego Melcon, MD, PhD, University Hospital Vall d'Hebron, Barcelona, Spain; Susanne Andrea Gatz, MD, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom; Marie-Cécile Le Deley, MD, Centre Oscar Lambret, Lille, France; Kieran McHugh, MD, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom; Alicia Probst, MSc, and Nathalie Rocourt, MD, Centre Oscar Lambret, Lille, France; Rick R. van Rijn, MD, PhD, Amsterdam University Medical Centers, Amsterdam, the Netherlands; Véronique Minard-Colin, MD, PhD, Department of Pediatric and Adolescent Oncology, INSERM U1015, Gustave Roussy, Université Paris-Saclay, Villejuif, France; and Julia C. Chisholm, MD, Children and Young People's Unit, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton, United Kingdom.