Clofarabine, Melphalan, and Thiotepa Followed By a Donor Stem Cell Transplant in Treating Patients With High-Risk and/or Advanced Hematologic Cancer or Other Disease

DISEASE CHARACTERISTICS:

* Histologically or cytologically confirmed diagnosis of 1 of the following:

  * Acute myelogenous leukemia, meeting 1 of the following criteria:

    * In first complete remission (CR), meeting 1 of the following criteria:

      * Poor risk \[no t(15,17), inv 16, or t(8,21)\]
      * Not a candidate for total body irradiation (TBI)
      * Any infant in first CR
    * In second CR, meeting the following criteria:

      * All patients
    * In more than second CR OR relapsed/refractory disease, meeting the following criteria:

      * All patients
      * Blast percentage \> 5% and \< 25% in bone marrow (BM) at the time of stem cell transplantation (SCT)
  * Acute lymphoblastic leukemia, meeting 1 of the following criteria:

    * In first CR, meeting 1 of the following criteria:

      * Poor risk \[t(9;22), t(4;11) AND no CR after 7-28 days of induction\]
      * Not a candidate for TBI
      * Any infant in first CR
    * In second CR, meeting the following criteria:

      * All patients
    * In more than second CR OR relapsed/refractory disease, meeting the following criteria:

      * All patients
      * Blast percentage \> 5% and \< 25% in BM at the time of SCT
    * Acute undifferentiated or biphenotypic leukemia, meeting the following criteria:

      * All patients
      * Blast percentage \> 5% and \< 25% in BM at the time of SCT
    * Chronic myelogenous leukemia, meeting the following criteria:

      * All patients
      * In first chronic phase
    * Myelodysplastic syndrome, meeting 1 of the following criteria:

      * Primary high risk disease

        * Stage \> RAEB1
      * Secondary high risk disease

        * All patients
        * Any stage
      * Juvenile myelomonocytic leukemia

        * All patients
* No doubling of peripheral blast counts within a period of 2 weeks
* No active CNS disease
* HLA-compatible donor available meeting 1 of the following criteria:

  * Related donor

    * Genotypically or phenotypically matched at ≥ 7 or 8 of HLA-A, -B, -C and -DRB1 alleles
  * Unrelated donor meeting 1 of the following criteria:

    * 8 of 8 alleles matched
    * For patients \< 18 years old only: 7 or 8 alleles matched with the mismatch at only 1 HLA-A, -B, -C, or -DRB1 allele
* Two HLA-compatible unrelated cord blood (UCB) units available meeting the following criteria:

  * HLA-matched minimally at 4 of 6 HLA-A, HLA-B, and DRB1 allele

    * HLA-A and HLA-B matched at intermediate resolution by molecular technique
    * DRB1 allele matched at high resolution by molecular technique
  * Both matched UCB units with cryopreserved nucleated cell dose ≥ 1.5 x 10\^7/kg

PATIENT CHARACTERISTICS:

* Karnofsky OR Lansky performance status 70-100%
* SGOT \< 2 times upper limit of normal
* Bilirubin \< 1.5 mg/dL (unless there is liver disease involvement)
* Creatinine normal OR creatinine clearance \> 60 mL/min
* LVEF \> 50% at rest OR shortening fraction ≥ 29%
* Patients with asymptomatic pulmonary disease with no prior risk factors OR symptomatic pulmonary disease with diffusion capacity \> 50% of predicted (corrected for hemoglobin) are eligible
* No active uncontrolled viral, bacterial, or fungal infection
* No known HIV I or II positivity
* No known human T-cell lymphotrophic virus I or II positivity
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

* No hydroxyurea within the past 2 weeks
* No allogeneic or autologous stem cell transplantation within the past 6 months