1. on behalf of the Nordic Society of Paediatric Haematology and Oncology (NOPHO) Departments of Paediatrics, 1National Hospital of Norway, Oslo, Norway, 2Landspitalinn, Reykjavik, Iceland, 3Östra Sjukhuset, Gothenborg, Sweden, 4University of Helsinki, Helsinki, Finland, 5National Hospital of Denmark, Copenhagen, Denmark, and 6Karolinska Hospital, Stockholm, Sweden