Donor Stem Cell Transplant in Treating Patients With Hematologic Cancer, Metastatic Kidney Cancer, or Aplastic Anemia

OBJECTIVES: Primary * Determine the treatment-related mortality (TRM) rate at 100 days in patients with hematologic malignancy, metastatic renal cell carcinoma, or aplastic anemia undergoing nonmyeloablative allogeneic stem cell transplantation using matched unrelated donors. Secondary * Determine the TRM at 12 months in patients treated with this regimen. * Determine the 6-month engraftment rate in patients treated with this regimen. * Determine 1-year overall survival of patients treated with this regimen. OUTLINE: * Nonmyeloablative preparative regimen: Patients receive fludarabine IV over 30 minutes on days -7 to -3, busulfan\* IV over 6 hours on days -4 and -3, and anti-thymocyte globulin IV over 6-10 hours on days -4 to -1. NOTE: \*Patients with aplastic anemia receive cyclophosphamide IV over 2 hours on days -6 to -3 instead of busulfan. * Allogeneic stem cell reinfusion: Patients undergo allogeneic bone marrow or peripheral blood stem cell transplantation on day 0. Patients then receive filgrastim (G-CSF) subcutaneously daily beginning on day 7 and continuing until blood counts recover. * Graft-vs-host disease (GVHD) prophylaxis: Patients receive tacrolimus orally twice daily or IV continuously beginning on day -2 and continuing for approximately for 6-12 months after transplantation. Patients also receive mycophenolate mofetil orally or IV twice daily on days 0 to 60 and methotrexate IV on days 1, 3, 6, and 11\*\*. NOTE: \*\*Patients with aplastic anemia receive methotrexate IV on days 1, 3, and 6 (not day 11). * Donor lymphocyte infusion (DLI): After day 180, patients with no evidence of active GVHD may receive DLI. A second DLI may be infused \> 8 weeks after the first in the absence of disease response or GVHD. After completion of study treatment, patients are followed periodically for at least 2 years. PROJECTED ACCRUAL: A total of 35 patients will be accrued for this study.