Patients with verified CNS disease receive weekly intrathecal (IT) methotrexate until 2 consecutive clear cerebrospinal fluid samples have been obtained. Cranial radiotherapy is administered over 15-21 days during weeks 5-8 concurrently with methotrexate IT in the appropriate regimen. Following radiotherapy, these patients receive monthly methotrexate IT for 1 year and then every 3 months until the end of therapy.