Cancer is the leading cause of death by disease in children under the age of 15 years. Brain tumors and acute lymphoblastic leukemia (ALL) are the two most common forms of pediatric cancer, collectively accounting for more than half of all newly diagnosed cases annually. Most research into the neuropsychological sequelae of pediatric cancer and its associated treatment has involved the study of ALL and brain tumors because of their high prevalence as well as their greater associated neuropsychological morbidity. This morbidity has become increasingly prevalent as survival rates for ALL and brain tumors have improved over the last several decades.

The neuropsychological sequelae of pediatric cancer extend into adolescence and adulthood and are not only associated with the cancer itself but the treatments employed, including surgical intervention, chemotherapy, cranial/craniospinal radiation therapy (CRT), or a combination of these treatments. Other disease- and treatment-related outcome moderators include neurologic complications (e.g., intracranial bleeding, hydrocephalus, leukoencephalopathy) and sensorimotor deficits related to the primary disease and/or to iatrogenic effects. CRT, in particular, has been one of the greatest contributors to improved survival in the treatment of brain tumors and higher risk forms of ALL, but it has also been associated with numerous neurologic and neurocognitive effects that vary according to the extent and location of CNS involvement, size of area irradiated, and total dose administered. Intrathecal and high-dose intravenous chemotherapies, particularly methotrexate, are now routinely employed without adjuvant radiation in the treatment of standard-risk ALL. While evidence regarding the neuropsychological risk associated with such isolated chemotherapy is mixed, it is generally acknowledged that both intrathecal chemotherapy and the chemotherapy agents administered in the treatment of various brain tumors have a less significant effect on neuropsychological outcome than does CRT.