1. Department of Epidemiology and Biostatistics, School of Public Health, Texas A&M University, College Station, TX 77843, USA
2. Department of Epidemiology and Cancer Control, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
3. School of Public Health, University of Alberta, Edmonton, AB T6G 2R3, Canada
4. Division of Haematology/Oncology, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
5. Department of Oncology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA