Umbilical Cord Blood Transplant, Cyclophosphamide, Fludarabine, and Total-Body Irradiation in Treating Patients With Hematologic Disease

OUTLINE: Patients are assigned to 1 of 2 arms. ARM I: Patients receive myeloablative conditioning comprising fludarabine intravenously (IV) over 30 minutes on days -8 to -6, cyclophosphamide IV on days -7 and -6, and undergo high-dose TBI twice daily (BID) on days -4 to -1. Patients then undergo single- or double-unit UCBT on day 0. ARM II: Patients receive myeloablative conditioning comprising fludarabine IV over 30-60 minutes on days -6 to -2, cyclophosphamide IV on day -6, thiotepa IV over 2-4 hours on days -5 and -4, and middle-intensity TBI once daily (QD) on days -2 and -1. Patients then undergo single- or double-unit UCBT on day 0. Patients receive GVHD prophylaxis comprising cyclosporine IV over 1 hour every 8 or 12 hours, then cyclosporine orally (PO) (if tolerated), on days -3 to 100 with taper on day 101. Patients also receive mycophenolate mofetil IV every 8 hours on days 0 to 7 and then PO (if tolerated) three times daily (TID) on days 8-30. Mycophenolate mofetil is tapered to BID on day 30 or 7 days after engraftment if there is no acute GVHD, and then tapered over 2-3 weeks beginning on day 45 (or 15 days after engraftment if engraftment occurred \> day 30) after engraftment if there continues to be no evidence of acute GVHD. After completion of study treatment, patients are followed up at 6 months, 1 year, and 2 years.