Antimetaboliths in the prophylaxis and treatment of central nervous system leukemia

The results of the administration of two antimetabolites, methotrexate (MTX) and cytosine arabinoside (Ara-C), for the prevention and treatment of established central nervous system (CNS) disease in children with acute lymphoblastic leukemia are discussed. Two protocols (L-2 and L-10) for the management of patients with acute lymphoblastic leukemia have been developed. In the L-2 protocol, prophylaxis consists of repeated intralumbar injections of MTX alone, and in the L-10 regimen, both MTX and Ara-C are administered; for the patients with an initial leukocyte count of greater than or equal to 25,000/mm3, the two drugs are given intraventricularly instead of by the usual intralumbar route. In the treatment of established CNS leukemia, intralumbar MTX and Ara-C in addition to CNS irradiation are employed; for maintenance, periodic intraventricular MTX injections are given. Of the 70 children receiving the L-2 protocol, four developed CNS leukemia and in a fifth patient, CNS and bone marrow relapse were concurrent. Among the 31 children receiving the L-10 regimen, CNS disease has been observed in only one child. Of the five children treated for the established CNS leukemia, recurrence was observed in two at 19 and 29 months after remission; the other three remain in remission for 2, 15, and 39 months, respectively.