Donor Umbilical Cord Blood Stem Cell Transplant in Treating Patients With Hematologic Malignancies

RATIONALE: Giving chemotherapy before a donor umbilical cord blood transplant (UCBT) helps stop the growth of cancer and abnormal cells and helps stop the patient's immune system from rejecting the donor's stem cells. When the stem cells from an unrelated donor, that do not exactly match the patient's blood, are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving antithymocyte globulin before transplant and cyclosporine and mycophenolate mofetil after transplant may stop this from happening. PURPOSE: This phase II trial is studying how well donor umbilical cord blood stem cell transplant works in treating patients with hematologic malignancies.

PRIMARY OBJECTIVES: 1\. To establish the day +180 overall survival after a myeloablative unrelated double unit UCBT in a single institution setting. SECONDARY OBJECTIVES: 1. To determine the rates of hematologic and immune reconstitution in patients with high risk hematologic malignancies, who are undergoing myeloablative chemotherapy followed by infusion of double unit UCBT. 2. To determine the contribution of each umbilical cord unit to immune reconstitution with a focus on both initial (day +21 BM, and +28 PB) and sustained engraftment (day +100 BM; PB at +14, +21, +28, +35, +42, +60, +100, +180, +1 and 2 years). 3. To determine the probability of overall survival and disease free survival at one and two years. 4. To describe the incidence of disease recurrence at one and two years in patients post UCBT. 5. To describe the incidence of acute GVHD and chronic GVHD at 100 days and at one year, respectively. 6. To determine the incidence of day 100 and 180 treatment related mortality. 7. To determine the incidence of serious infectious complications in the first year after transplant. 8. To determine the incidence of donor-derived neutrophil and platelet recovery. 9. To determine the incidence of secondary lymphoproliferative diseases following transplantation with umbilical cord blood. OUTLINE: PREPARATIVE REGIMEN: Patients receive oral busulfan every 6 hours on days -8 to -5, cyclophosphamide IV on days -4 to -3, and anti-thymocyte globulin or methylprednisolone IV on days -3 to -1. TRANSPLANTATION: Patients undergo double-unit umbilical cord blood allogeneic stem cell transplantation on day 0. GRAFT-VS-HOST DISEASE PROPHYLAXIS: Beginning on day -2, patients receive cyclosporine IV and taper beginning on day 100. Patients also receive mycophenolate mofetil IV or orally every 8 hours on days -3 to 45. After completion of study treatment, patients are followed periodically.