[1] Charite, Campus Virchow Klinikum, Klin Padiatrie MS Onkol Hamatol, Dept Paediat Oncol & Haematol, D-13353 Berlin, Germany
[2] Charite, Inst Social Med Epidemiol & Hlth Econ, D-13353 Berlin, Germany
[3] Univ Dusseldorf, Clin Pediat Oncol Hematol & Clin Immunol, Fac Med, Ctr Child & Adolescent Hlth, D-40225 Dusseldorf, Germany
[4] Erlangen Univ Hosp, Dept Paediat, Dept Immunol & Oncol, Erlangen, Germany
[5] Univ Childrens Hosp Muenster, Dept Paediat Haematol & Oncol, Munster, Germany
[6] Motol Univ Hosp, Dept Paediat Haematol & Oncol, Prague, Czech Republic
[7] St Anna Childrens Hosp, Childrens Canc Res Inst, A-1090 Vienna, Austria
[8] Univ Frankfurt Hosp, Dept Haematol, Frankfurt, Germany