Cancer is the leading cause of death by disease in children under the age of 15 years (National Cancer Institute Research on Childhood Cancers, Cancer Facts). Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer, comprising approximately 40% of all diagnosed cases (Margolin & Poplack, 1997). Brain tumors are the second most frequent malignancy of childhood and the most common of the solid tumors (Ries et al., 2004). Brain tumors and other central nervous system (CNS) cancers account for approximately 20% of all childhood cancers (Sklar, 2002).
Given their higher prevalence amongst childhood cancers and their associated neuropsychological risk, most research into the neuropsychological sequelae of childhood cancer and its related treatment has involved the study of ALL and brain tumors. Such research has become increasingly important as neuropsychological morbidity has increased with the substantial increase in survival rates that has accompanied advances in detection and treatment over the last several decades. Estimated 10-year survival rates for children diagnosed with CNS tumors from 1995 to 1999 were approximately 70% (Brenner, 2003). Five-year survival rates for children with ALL under age 19 now exceed 70% (Ries et al., 2004).
Treatment interventions and associated neuropsychological outcome
Treatment of childhood cancers involving or at risk of involving the CNS varies considerably and is dependent on such factors as tumor type, grade of malignancy, location of the tumor, extent of CNS involvement, and age of the child.