[1] Univ Groningen, Univ Med Ctr Groningen, Beatrix Childrens Hosp, Dept Pediat Oncol Hematol, Groningen, Netherlands
[2] Princess Maxima Ctr Pediat Oncol, Utrecht, Netherlands
[3] Emma Childrens Hosp, Acad Med Ctr, Dept Pediat Oncol, Amsterdam, Netherlands
[4] Dutch Childhood Oncol Grp, Utrecht, Netherlands
[5] Univ Groningen, Univ Med Ctr Groningen, Dept Epidemiol, Groningen, Netherlands