 INDUCTION THERAPY: Patients with less than 20 tumor reduction follow the group C induction phase described below. Patients with at least 20 tumor reduction receive 1 course of the COPADM regimen: vincristine IV and methotrexate IV over 4 hours on day 0; PRED or MePRDL IV or orally on days 0-7; leucovorin calcium IV or orally every 6 hours for 12 doses on days 1-3; doxorubicin IV over 30-60 minutes on day 1; cyclophosphamide IV over 15 minutes every 12 hours on days 1-3; methotrexate IT and hydrocortisone IT on days 1 and 5; and filgrastim G-CSF subcutaneously SC beginning on day 6 and continuing until blood counts recover. 