Patients will be randomly assigned with equal probability to one of the study's treatment arms. neither the doctor nor the patient will be able to choose which regimen is received. eligibility restrictions and the use of stratification will ensure that similar patient populations are being compared, and the number of patients required for the study will increase the certainty that any differences in outcome or side effects are indeed due to the type of treatment they received.
arm a: HCT Conditioning Regimen with Bu-CY-MeL
arm B: HCT Conditioning with Bu-FLu
* Central line (iV)
* Frequent blood draws to monitor blood count and chemistry
* urine test
* ultrasounds to measure spleen and liver
* Bone Marrow aspirations
* Tests to see if donor stem cells have settled into the bone marrow
* Cytogenetic testing to look for abnormalities in leukemia cells
* Pregnancy test
Genetic tests to identify abnormal changes in four genes. additional blood draws and bone marrow aspiration for clinical tests and for future medical research. if the patient agrees, spleen and skin samples may also be taken for future medical research.
* Patients must be >= 3 months and <= 18 years at the time of study enrollment.
* Patients must have a strong clinical suspicion of JMML as defined in the protocol. Specifically, eligible patients must have all of the following: Splenomegaly, Absolute monocyte count (AMC) > 1000/[MICRO-SYMBOL]L, and Blasts in PB/BM < 20%.
For the 7-10% of patients without splenomegaly, the diagnostic entry criteria must include all other features described above and at least 2 of the following criteria:
* Circulating myeloid precursors
* WBC > 10,000/[MICRO-SYMBOL]L
* Increased fetal hemoglobin (HgbF) for age
* GM-CSF hypersensitivity
b. Patients must have been previously diagnosed with JMML (per Section 4.3.1 of the protocol).
* Patients must be previously untreated with HCT. Prior treatment with targeted agents are allowed.