Treatment Block 2: Patients receive methotrexate IT on days 1 and 22, cyclophosphamide IV over 30 minutes and etoposide IV over 2 hours on days 1-5, and filgrastim (G-CSF) subcutaneously (SC) beginning on day 6 and continuing until blood counts recover. Patients also receive methotrexate IV over 24 hours on day 22 followed by leucovorin calcium IV every 6 hours on days 24 and 25. Ph-positive patients receive imatinib mesylate PO on days 1-14.