This chapter reviews neuropsychological late effects associated with childhood cancer and its treatment. The study of late effects presupposes that patients are long-term survivors, if not permanently cured, of their disease. Late effects are temporally defined as occurring after the successful completion of medical therapy, usually 2 or more years from the time of diagnosis, and it is generally assumed that late effects are chronic, if not progressive, in their course. This definition serves to separate late effects from those effects of disease and treatment that are acute or subacute and time limited, such as chemotherapy-induced nausea and vomiting or temporary cognitive changes induced by cancer therapy. Research interest in neuropsychological outcomes, as well as neurological and other functional late effects, has shown an increase commensurate with improvements in effective therapy. For example, 30 years ago when few children were cured of acute lymphoblastic leukemia (ALL), questions related to the ultimate academic or vocational performance of long-term survivors were trivial compared to the need for improved therapy. In contrast, today more than 80% of children diagnosed with ALL can be cured, and issues related to their quality of life as long-term survivors have now received increased emphasis. There is at least comparable attention to neuropsychological status in primary brain tumors. We first provide a brief medical background on the two most frequent forms of childhood cancer, ALL and malignant brain tumors, followed by a review of the current neuropsychological literature. The literature review provides an in-depth analysis of the types of cognitive impairments observed and known or suspected risk factors for impairments. When neurobiological substrates are known, particularly from neuroimaging studies, they are discussed. Finally, we conclude the review with sections that discuss current recommendations for a core battery of neuropsychological assessment of survivors and recommendations for future research. Approximately 20,000 children and adolescents under the age of 20 years were diagnosed with cancer in 1999 (Steen & Mirro, 2000). The most commonly diagnosed cancer in this age group is ALL, a malignant disorder of lymphoid cells found in the bone marrow that migrates to virtually every organ system, including the central nervous system (CNS), via the circulatory system. ALL accounts for one fourth of all childhood cancers and 75% of all cases of childhood leukemia (Margolin, Steuber, & Poplack, 2002).
Childhood cancer: Survival, treatment modalities, late effects and improvements over time