[1] Emory Univ, Dept Pediat, Childrens Healthcare Atlanta, Atlanta, GA 30322 USA
[2] St Jude Childrens Res Hosp, Dept Biostat, Memphis, TN 38105 USA
[3] St Jude Childrens Res Hosp, Dept Epidemiol & Canc Control, Memphis, TN 38105 USA
[4] St Jude Childrens Res Hosp, Dept Oncol, Memphis, TN 38105 USA
[5] City Hope Natl Med Ctr, Dept Populat Sci, Duarte, CA 91010 USA
[6] Hosp Sick Children, Dept Paediat, Div Haematol Oncol, Toronto, ON M5G 1X8, Canada
[7] Univ Toronto, Toronto, ON, Canada
[8] Univ Michigan, CS Mott Childrens Hosp, Dept Pediat & Communicable Dis, Ann Arbor, MI 48109 USA