Umbilical Cord Blood (UCB) Transplantation in Pediatric Patients With High Risk Leukemia and Myelodysplasia

Inclusion Criteria:

* Patients must be up to 21 years of age
* Patients cannot receive total body irradiation (TBI) because of:

  * Young age - \< 2 years at diagnosis of leukemia resulting in an age \< 4 years at transplantation (due to risk of severe growth retardation and brain damage).
  * Inability to tolerate TBI because of prior radiation or organ toxicity.
  * Refractory/multiply relapsed leukemia, for which a traditional TBI/cyclophosphamide regimen would unlikely lead to a successful outcome.
* Patients must have a partially human leukocyte antigen (HLA)-matched UCB unit. Unit must be HLA-matched minimally at 4 of 6 HLA-A and B (at intermediate resolution by molecular typing) and DRB1 (at high resolution by molecular typing) loci with the patient. The unit must deliver a pre-cryopreserved nucleated cell dose of at least 2.5 x 10\^7 per kilogram.
* Acute myelogenous leukemia (AML) at the following stages:

  * High risk first complete remission (CR1), defined as:

    * Having preceding myelodysplasia (MDS)
    * High risk cytogenetics (High-risk cytogenetics: del (5q) -5, -7, abn (3q), t (6;9) complex karyotype (\>= 5 abnormalities)
    * Requiring \> 2 cycles chemotherapy to obtain CR;
  * Second or greater CR.
  * First relapse with \< 25% blasts in bone marrow.
* Patients with therapy-related AML whose prior malignancy has been in remission for at least 12 months.
* Acute lymphocytic leukemia (ALL) at the following stages:
* High risk first remission, defined as:

  1. Ph+ ALL; or,
  2. Myeloid/lymphoid leukemia (MLL) rearrangement with slow early response \[defined as having M2 (5-25% blasts) or M3 (\>25% blasts on bone marrow examination on Day 14 of induction therapy)\]; or,
  3. Hypodiploidy (\< 44 chromosomes or DNA index \< 0.81); or,
  4. End of induction M3 bone marrow; or,
  5. End of induction M2 with M2-3 at Day 42.
* High risk second remission, defined as:

  1. Bone marrow relapse \< 36 months from induction; or,
  2. T-lineage relapse at any time; or,
  3. Very early isolated central nervous system (CNS) relapse (6 months from diagnosis); or,
  4. Slow reinduction (M2-3 at Day 28) after relapse at any time.
* Any third or subsequent CR.
* Biphenotypic or undifferentiated leukemia in any CR or if in 1st relapse must have \< 25% blasts in bone marrow (BM).
* MDS at any stage.
* Chronic myelogenous leukemia (CML) in chronic or accelerated phase.
* All patients with evidence of CNS leukemia must be treated and be in CNS CR to be eligible for study.
* Patients ≥ 16 years old must have a Karnofsky score ≥ 70% and patients \< 16 years old must have a Lansky score ≥ 70%.
* Signed informed consent.
* Patients with adequate physical function as measured by:

  1. Cardiac: Left ventricular ejection fraction at rest must be \> 40%, or shortening fraction \> 26%
  2. Hepatic: Bilirubin ≤ 2.5 mg/dL; and alanine transaminase (ALT), aspartate transaminase (AST) and Alkaline Phosphatase ≤ 5 x upper limit of normal (ULN)
  3. Renal: Serum creatinine within normal range for age, or if serum creatinine outside normal range for age, then renal function (creatinine clearance or GFR) \> 70 mL/min/1.73 m2.
  4. Pulmonary: Diffusing capacity of the lungs for carbon monoxide (DLCO), Forced expiratory volume in 1 second (FEV1), Forced vital capacity (FVC) (diffusion capacity) \> 50% of predicted (corrected for hemoglobin); if unable to perform pulmonary function tests, then O2 saturation \> 92% of room air.

Exclusion Criteria:

* Pregnant (B-positive HCG) or breastfeeding.
* Evidence of HIV infection or HIV positive serology.
* Current uncontrolled bacterial, viral or fungal infection (currently taking medication and progression of clinical symptoms).
* Autologous transplant \< 6 months prior to enrollment.
* Prior autologous transplant for the disease for which the UCB transplant will be performed.
* Allogeneic hematopoietic stem cell transplant \< 6 months prior to enrollment.
* Active malignancy other than the one for which the UCB transplant is being performed within 12 months of enrollment
* Active CNS leukemia.
* Requirement of supplemental oxygen.
* HLA-matched related donor able to donate.