1. Swiss Childhood Cancer Registry, Institute of Social and Preventive Medicine; University of Bern; Finkenhubelweg 11; 3012; Bern; Switzerland
2. Department of Oncology; University Children's Hospital; Steinwiesstrasse 75; 8032; Zurich; Switzerland
3. Department of Pediatric Oncology and Hematology; Children's Hospital; 6000; Lucerne; Switzerland
4. Department of Pediatrics; University of Bern, Inselspital; 3010; Bern; Switzerland