Study for Safety and Efficacy Evaluation of Imatinib Mesylate in Children With Acute Lymphoblastic Leukemia (ALL) Philadelphia Chromosome-positive (Ph+)

Inclusion Criteria: 1. Diagnose: therapy-naïve ALL, except for patients that performed Induction for ALL (33 days) exactly as this protocol and; documented Ph+, to be confirmed by conventional cytogenetic - t(9;22) (q34;q11) or FISH and/or gene BCR-ABL presence by RT-PCR or FISH. 2. Female patients of childbearing age, should have pregnancy test (blood βhCG) performed before treatment initiation. Effective contraception must be used during treatment. Pregnant women won't be included. 3. Life expectation \> 8 weeks. 4. Medications: antineoplastic treatment-naïve, including corticotherapy, except for patients that performed Induction for ALL (33 days) exactly as this protocol. 5. Signed ICF by child legal responsible. 6. Laboratory: renal function (serum creatinine ≤ 1,5 x ULN and/or Clearance ≥70 ml/min/1,73m2), hepatic function (total bilirubin ≤ 1,5 x ULN, TGP/TGO \< 10 x ULN and albumin \> 2 g/dl. Exclusion Criteria: 1. Any inclusion criteria missing. 2. Pregnant patient or breastfeeding. 3. Patient considered incapable to follow purposed treatment. 4. Subject with infectious process, in activity, grade IV.