1. Finnish Cancer Registry, Helsinki, Finland
2. New Children’s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
3. Boston Children’s Cancer and Blood Disorders Center, Dana Farber Cancer Institute, Boston, MA, USA
4. Department of Public Health, University of Helsinki, Helsinki, Finland
5. School of Health Sciences, University of Tampere, Tampere, Finland
6. Division of Pediatric Hematology, Oncology and Stem Cell Transplantation, Helsinki University Hospital and University of Helsinki, Helsinki, Finland