Protocol I Cytoreductive prephase: Prednisone (PDN) on days 1-7 and one dose of methotrexate (MTX) intrathecal (IT) on day 1 Protocol IA: Prednisone (PDN) on days 8 to 28 (21 days); vincristine (VCR) on days 8, 15, 22, 29 (4 doses); daunorubicin (DNR) on days 8, 15, 22 and 29 (4 doses); pegylated L-asparaginase (PEG-L-ASP) on days 12 and 26; MTX IT on days 12 and 33 and in case of blast cells in cerebrospinal fluid at diagnosis additional IT MTX is given on days 19 and 26.