[1] Univ Tennessee, Ctr Hlth Sci, Coll Med, Memphis, TN 38163 USA
[2] Cornell Univ, Weill Med Coll, New York, NY 10021 USA
[3] St Jude Childrens Res Hosp, Dept Epidemiol & Canc Control, 332 N Lauderdale St, Memphis, TN 38105 USA
[4] Univ Mississippi, Sch Med, Jackson, MS 39216 USA
[5] Brown Univ, Alpert Brown Med Sch, Providence, RI 02903 USA
[6] St Jude Childrens Res Hosp, Dept Oncol, 332 N Lauderdale St, Memphis, TN 38105 USA