- Determine the frequency, extent, and rate of donor (myeloid and lymphoid) engraftment in patients with serious hematologic malignancies treated with nonmyeloablative conditioning regimen comprising fludarabine, cyclophosphamide, and low-dose total-body irradiation followed by unrelated allogeneic umbilical cord blood transplantation and post-transplant immunosuppression comprising cyclosporine and mycophenolate mofetil.