1. Department of Hygiene, Epidemiology and Medical Statistics Medical SchoolNational and Kapodistrian University of AthensAthens, Greece
2. Department of Pediatric Hematology–Oncology“Pan. & Agl. Kyriakou” Children's HospitalAthens Greece
3. Pediatric Hematology/Oncology Unit, First Department of PediatricsUniversity of Athens, “Agia Sofia” Children's HospitalAthens Greece
4. Department of Pediatric Hematology–Oncology“Agia Sofia” Children's HospitalAthens Greece
5. Department of Pediatric Hematology and OncologyHippokration HospitalThessaloniki Greece
6. 2nd Hematology Oncology Unit, 2nd Pediatric DepartmentAristotle University of Thessaloniki, AHEPA HospitalThessaloniki Greece
7. Department of Pediatric Hematology–OncologyUniversity of CreteHeraklion Greece
8. Department of Pediatric Hematology–Oncology“Mitera” Children's HospitalAthens Greece
9. North Region Cancer Registry of Portugal (RORENO), Portuguese Institute of OncologyPorto Portugal
10. Registo Oncológico Regional do Centro (ROR‐Centro), Instituto Português de Oncologia de Coimbra Francisco Gentil, E.P.E.Coimbra Portugal
11. The Oncology Institute “Prof. Dr. Ion Chiricuţă”Cluj‐Napoca Romania
12. Health Monitoring Unit, Ministry of HealthNicosia Cyprus
13. Department for Policy in Health – Health Information and ResearchMalta National Cancer RegistryPieta Malta
14. Izmir Cancer Registry, Izmir Hub, Izmir and HacettepeUniversity Institute of Public HealthAnkara Turkey
15. Regional Cancer Registry, National Institute of Public HealthIasi Romania
16. Croatian Institute of Public Health, Croatian National Cancer RegistryZagreb Croatia
17. Andrija Štampar School of Public Health, School of MedicineUniversity of ZagrebZagreb Croatia
18. Wielkopolskie Centrum Onkologii, Poznan University of Medical SciencesPoznan Poland
19. Cancer Registry of Slovenia, Institute of Oncology LjubljanaLjubljana Slovenia
20. Belarusian Research Center for Paediatric Oncology, Haematology and ImmunologyChildhood Cancer Subregistry of BelarusMinsk Belarus
21. National Cancer Registry of Ukraine, National Institute of CancerKiev Ukraine
22. Fourth Department of PediatricsMedical School, General Hospital “Papageorgiou”, Aristotle University of ThessalonikiThessaloniki Greece
23. International Agency for Research on Cancer, World Health OrganizationLyon France