Cytarabine and Clofarabine in Treating Patients With Refractory or Relapsed Acute Myeloid Leukemia or Acute Lymphoblastic Leukemia

DISEASE CHARACTERISTICS: Pathologic confirmation of acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) No M3 AML Meets 1 of the following criteria: In first relapse In second relapse after a second complete remission (CR) that lasted ≥ 3 months Refractory to initial induction therapy No symptomatic CNS involvement PATIENT CHARACTERISTICS: ECOG performance status ≤ 2 Creatinine < 2 mg/dL Bilirubin ≤ 2 mg/dL AST and ALT ≤ 4 times upper limit of normal Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for 2 weeks after completing study treatment Ejection fraction ≥ 45% by echocardiogram No active, uncontrolled systemic infection considered opportunistic, life-threatening, or clinically significant No psychiatric disorders that would interfere with giving consent, study participation, or follow-up procedures No other severe concurrent disease that would preclude study treatment PRIOR CONCURRENT THERAPY: At least 1 week since prior therapy and recovered No other concurrent chemotherapy Hydroxyurea to control WBC count before starting study treatment allowed No concurrent corticosteroids unless used for diseases other than leukemia No concurrent palliative radiotherapy No concurrent growth factors (e.g., epoetin alfa, filgrastim [G-CSF], or sargramostim [GM-CSF]) in patients with AML