Cytosine Arabinoside and Mitoxantrone for Patients With Juvenile Myelomonocytic Leukemia Receiving Repeat Stem Cell Transplantation

Inclusion Criteria:

* Patients age 0-18 with juvenile myelomonocytic leukemia (JMML) who have relapsed or have residual disease after allogeneic HCT. Residual disease is defined as failure to eradicate original disease without prior documentation of remission. Relapse is defined as reappearance of i) leukocytosis with absolute monocytosis \>1 x 10\^8/L, ii) presence of immature myeloid cells in the peripheral circulation in two consecutive bone marrow specimens taken at least one month apart, or iii) presence of clonal cytogenetic abnormality. The diagnosis of relapse will be supported by the return of an abnormal cytogenetic marker (if present at diagnosis) or the presence of host cells by RFLP or other method.
* Patients should be at least 6 months from first hematopoietic cell transplant (HCT) if clinically stable. (If JMML is rapidly progressive, second HCT may be performed earlier).

  * Adequate major organ function including:

    * Cardiac: ejection fraction ≥45%
    * Pulmonary: FEV \>50%, DLCO \>50%
  * Renal: creatinine clearance ≥40 mL/min

    * Hepatic: no clinical evidence of hepatic failure (e.g. coagulopathy, ascites)
  * Karnofsky performance status ≥70% or Lansky score ≥50%
* Written informed consent.

Exclusion Criteria:

* Active uncontrolled infection within one week of HCT.