[1] Univ Minnesota, Div Epidemiol & Community Hlth, Sch Publ Hlth, Minneapolis, MN 55454 USA
[2] Univ Minnesota, Sch Med, Dept Pediat, Div Hematol Oncol Bone Marrow Transplantat, Minneapolis, MN 55454 USA
[3] Univ Minnesota, Ctr Canc, Prevent Etiol Program, Minneapolis, MN 55454 USA
[4] Univ Minnesota, Ctr Canc, Transplant Biol & Therapy Res Program, Minneapolis, MN 55454 USA
[5] St Jude Childrens Hosp, Dept Epidemiol & Canc Control, Memphis, TN 38105 USA
[6] Univ Michigan, Sch Med, Dept Pediat, Child Hlth Evaluat & Res CHEAR Unit, Ann Arbor, MI USA