1. Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK
2. Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
3. Present address: KUNO Children's Hospital, Pediatric Hematology, Oncology and Stem Cell Transplantation, University Medical Center Regensburg, Regensburg, Germany
4. Department of Pediatric Oncology and Hematology, Erasmus MC‐Sophia Children's Hospital, Rotterdam, The Netherlands
5. Department of Pediatrics, University Medical Center Schleswig‐Holstein, Campus Kiel, Kiel, Germany
6. North of England Stem Cell Institute, Newcastle University, Newcastle upon Tyne, UK