Adverse events

All patients received Busulfan as per standard of care. Busulfan test dose can be administered either as an outpatient prior to admission or as an inpatient on Day -10. Busulfan pharmacokinetics will be performed with the test dose and the first dose on Day -7 per standard of care. The doses of Days -6, -5, and -4 will be subsequently adjusted to target an AUC of 4,000 microMol.min-1. In the event that PK adjusting were not possible a dose of busulfan of 130 mg/m2 will be administered. GVHD PROPHYLAXIS: All patients also receive mycofenolate mofetil IV over 2 hours or PO BID on days -3 with a taper beginning on day 100 in the absence of GVHD, tacrolimus IV or PO starting on day -2 for 6 months in the absence of GVHD, and filgrastim-sndz SC QD starting on day 0 until white blood count begins to recover. Anti-Thymocyte Globulin: Given IV Busulfan: Given IV Clofarabine: Given IV Cyclophosphamide: Given IV Filgrastim-sndz: Given SC Fludarabine: Given IV Melphalan: Given IV Mycophenolate Mofetil: Given IV or PO Rituximab: Given IV Tacrolimus: Given IV Total-Body Irradiation: Undergo total body irradiation Umbilical Cord Blood Transplantation: Undergo cord blood transplant