Pediatric cancer in the United States: the Children's Oncology Group Epidemiology Research Program.

Over 8,500 children under age 15 years are diagnosed with cancer each year in the United States (1). Unlike adults, where epithelial tumors predominate, the most common types of cancer in children include the leukemias and lymphomas and the tumors of the central and sympathetic nervous systems, soft tissue, bone, and kidney. The overall incidence rate for childhood cancers has increased significantly by almost 33% during the period 1975 to 2001 (1), although, in more recent years, the rate has been leveling off. Only f5% of childhood cancers can primarily be attributed to a genetic predisposition (2). With the exception of a few known risk factors including in utero exposure to radiation and prior chemotherapeutic agents (3), the etiology of most childhood cancer is unknown. Because of its rarity, epidemiologic studies of childhood cancer are challenging. In particular, using a case-control approach necessitates careful assembly of well-characterized cases, which requires cooperation among many hospitals and institutions and the identification of a feasible and valid control group. In this editorial, we highlight the current challenges and approaches to advancing our understanding of the etiology of childhood cancer.