1. From the Epidemiology and Biostatistics Section, Scientific Directorate, Department of Hematology-Oncology, and Laboratories of Diagnostic Pathology and Clinical Chemistry, Giannina Gaslini Children's Hospital, Genova; Department of Pediatrics, Universities of Bari, Bologna, Catania, Napoli, Padova, Palermo, Parma, Pisa, Torino, and Trieste; Departments of Pediatric Oncology, Bambino Gesù Children's Hospital, Roma; Childhood Cancer Registry of Piedmont, Torino; and National Cancer Institute, Milano, Italy.