Central nervous system disease in acute lymphoblastic leukemia: prophylaxis and treatment.

Improved treatment for acute lymphoblastic leukemia (ALL) has virtually eliminated testicular relapse. However, the control of central nervous system (CNS) leukemia remains a therapeutic challenge in childhood ALL, partly because of the late complications arising from cranial irradiation. In most current pediatric protocols, cranial irradiation (12 to 18 Gy) is given to 5% to 25% of patients--those with T-cell ALL, overt CNS disease (CNS3 status) or high-risk cytogenetics. CNS control is a less urgent concern in adults with ALL, in whom systemic relapse remains the major problem. With current approaches, approximately 2% to 10% of patients can be expected to develop CNS relapse. Children with B-cell precursor ALL who have a late CNS relapse (after an initial remission of 18 months or more) and did not receive cranial irradiation have an excellent outcome after retrieval therapy, with a 5-year event-free survival (EFS) rate approaching that in newly diagnosed patients. Innovative treatment options are needed for children who develop CNS relapses after a short initial remission or after receiving cranial irradiation, and in any adults with CNS leukemia at diagnosis or relapse.