[1] Washington Univ, Dept Pediat, Div Hematol Oncol, Sch Med, St Louis, MO 63110 USA
[2] Washington Univ, Sch Med, Dept Med, Bioeth Res Ctr, St Louis, MO 63110 USA
[3] St Jude Childrens Res Hosp, Dept Oncol, 332 N Lauderdale St, Memphis, TN 38105 USA
[4] St Jude Childrens Res Hosp, Div Qual Life & Palliat Care, 332 N Lauderdale St, Memphis, TN 38105 USA
[5] Dana Farber Canc Inst, Pediat Oncol, Boston, MA 02115 USA
[6] Dana Farber Canc Inst, Div Populat Sci, Boston, MA 02115 USA