Reduction in Central Nervous System Leukemia With a Pharmacokinetically Derived Intrathecal Methotrexate Dosage Regimen

enrolled on three major studies of acute lymphoblas-tic leukemia by participating institutions of the Chil-drens Cancer Study Group. Each study included a dif-ferent method of central nervous system (CNS) prophylaxis: (1) standard therapy with cranial irra-diation, 2400 rads, and intrathecal methotrexate at 12 mg/m 2 six times during consolidation (CCG-141); (2) a modification of CCG-141 in which the intrathe-cal methotrexate was initiated during induction (CCG-141A); and (3) a reduced cranial irradiation dose of 1800 rads with intrathecal methotrexate giv-en at the same frequency as in CCG-141A, with or without maintenance intrathecal methotrexate, but with a dosage regimen derived from CNS volume considerations rather than based on body surfac