Clofarabine and Cyclophosphamide in Treating Patients With Relapsed or Refractory Acute Leukemia, Chronic Myelogenous Leukemia, or Myeloproliferative Disorders

DISEASE CHARACTERISTICS: Histologically confirmed leukemia or myeloproliferative disorders, including 1 of the following: Acute myeloid leukemia (AML) of any subtype Treatment-related AML OR AML evolving from myeloproliferative disorders (MPD) or transformed from myelodysplastic syndrome Acute lymphocytic leukemia Acute progranulocytic leukemia Must not be eligible for arsenic or retinoic acid therapy Chronic myelogenous leukemia in accelerated phase or blast crisis High-risk MPD, including any of the following: Myelofibrosis Chronic myelomonocytic leukemia with 5%-19% blasts Relapsed or refractory juvenile myelomonocytic leukemia Relapsed and/or refractory disease with progressive disease since last therapy No more than 3 prior induction regimens with cytotoxic agents for adults Must be in second relapse for patients < 21 years of age PATIENT CHARACTERISTICS: ECOG performance status 0-2 (for adults) OR Lansky 50-100% (for pediatric patients) Bilirubin ≤ 1.5 mg/dL (may be elevated due to hemolysis in adult patients) AST and ALT ≤ 5 times upper limit of normal Creatinine ≤ 2.0 mg/dL (for adults) Normal renal function (for pediatric patients) Cardiac function normal as measured by MUGA scan or echocardiogram Not pregnant or nursing Negative pregnancy test Fertile patients must use effective barrier contraception during and for at least 6 months after completion of study treatment HIV negative No active graft-versus-host disease ≥ grade 2 No active, uncontrolled infection No fever No unstable CT scans of the lungs, sinuses, or abdomen within the past 4 weeks No arrhythmias (other than atrial flutter or fibrillation) requiring medication No dyspnea at rest or with minimal exertion No uncontrolled congestive heart failure No myocardial infarction within the past 3 months No history of severe coronary artery disease No other significant concurrent disease, illness, or psychiatric disorder that would compromise patient safety or compliance or interfere with consent, study participation, follow up, or interpretation of study results PRIOR CONCURRENT THERAPY: Must have recovered from all acute toxic effects from prior treatment More than 30 days since prior investigational cytotoxic agents At least 3 days since prior azacitidine, thalidomide, hydroxyurea, imatinib mesylate, or interferon At least 1 week since prior growth factors except epoetin alfa More than 3 weeks since any other prior anticancer therapy No concurrent chemotherapy, radiotherapy, or immunotherapy No other concurrent anticancer investigational or commercial agents No routine prophylactic use of a colony-stimulating factor (filgrastim [G-CSF] or sargramostim [GM-CSF]) Therapeutic use of colony-stimulating factors may be considered at the discretion of the investigator No prolonged use of corticosteroids to prevent or treat emesis or as a chemotherapeutic agent