1. Department of Pediatric and Adolescent Medicine, Turku University Hospital and Turku University, Turku, Finland;
2. Childhood Cancer Research Unit, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden;
3. Department of Pediatrics and Adolescence, Oulu University Hospital, Oulu, Finland;
4. School of Medicine, University of Tampere, Tampere, Finland