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Central nervous system (CNS) involvement is identified at the time of diagnosis in less than 5% of children with acute lymphoblastic leukemia (ALL) [1]. However, prior to the institution of adequate CNS prophylaxis, it was a major obstacle to cure in childhood ALL as 50-75% of patients would eventually relapse in the CNS [1, 2]. The routine use of CNS prophylaxis has improved the long-termprognosis of patients, and CNS relapse occurs in less than 10% of patients treated with contemporary protocols [3]. Effective means of CNS prophylaxis include cranial irradiation, intrathecal chemotherapy (IT), and high-dose systemic chemotherapy (HDCT) with agents that can cross the blood-brain barrier [4]. A risk-oriented approach has been developed for childhood CNS prophylaxis, in an attempt to reduce the occurrence of CNS relapse while minimizing the potentially serious adverse effects of radiotherapy and chemotherapy [4]. [ABSTRACT FROM AUTHOR]