1. Department of Pediatric Hematology and Oncology, Medical School Hannover, Hannover, Germany;
2. Department of Pediatric Hematology and Oncology, University Children's Hospital, Muenster, Germany;
3. St Anna Kinderspital and Childrens Cancer Research Institute, Vienna, Austria;
4. Kinderklinik Krankenanstalten Gilead, Bielefeld, Germany;
5. University Hospital Hamburg-Eppendorf, University Hamburg, Hamburg, Germany; and
6. Prof-Hess-Kinderklinik, Klinikum Bremen-Mitte, Bremen, Germany