Central nervous system involvement in adult acute lymphoblastic leukemia.

Central nervous system (CNS) involvement is identified at the time of diagnosis in less than 10% of adult acute lymphoblastic leukemia (ALL). These patients can attain long-term disease-free survival. CNS disease at presentation does not appear to be an independent poor prognostic factor. Because of the difficulty in treating CNS leukemia, innovative treatments and alternative delivery techniques are needed. The outcome in such patients is a reflection of an aggressive systemic and CNS-directed therapy. However, CNS toxicity represents the dose-limiting side effect of treatment. With effective CNS prophylaxis including intrathecal chemotherapy, high-dose systemic administration of certain agents and cranial irradiation, most adults with ALL without CNS disease at diagnosis may remain free of CNS leukemia. Leukemic relapse remains a major therapeutic problem and CNS involvement at the time of relapse occurs in 1-15% of cases. Adult ALL with CNS recurrence remains of poor prognosis and is generally associated with a systemic relapse.