[1] Yale Univ, Dept Pediat, Sect Pediat Hematol & Oncol, Sch Med, 330 Cedar St,LMP 2073,POB 208064, New Haven, CT 06520 USA
[2] Yale Sch Med, Dept Internal Med, Canc Outcomes & Publ Policy & Effectiveness Res C, New Haven, CT USA
[3] Univ Minnesota, Dept Pediat, Div Epidemiol & Clin Res, Minneapolis, MN 55455 USA
[4] Univ Texas MD Anderson Canc Ctr, Dept Pediat Patient Care, Div Pediat, Houston, TX 77030 USA
[5] Yale Univ, Dept Chron Dis Epidemiol, Sch Publ Hlth, New Haven, CT USA