Haploidentical Stem Cell Transplantation for Patients With Hematologic Malignancies

Blood and marrow stem cell transplant has improved the outcome for patients with high-risk hematologic malignancies. However, most patients do not have an appropriate HLA (immune type) matched sibling donor available and/or are unable to identify an acceptable unrelated HLA matched donor through the registries in a timely manner. Another option is haploidentical transplant using a partially matched family member donor. Although haploidentical transplant has proven curative in many patients, this procedure has been hindered by significant complications, primarily regimen-related toxicity including graft versus host disease (GVHD) and infection due to delayed immune reconstitution. These can, in part, be due to certain white blood cells in the graft called T cells. GVHD happens when the donor T cells recognize the body tissues of the patient (the host) are different and attack these cells. Although too many T cells increase the possibility of GVHD, too few may cause the recipient's immune system to reconstitute slowly or the graft to fail to grow, leaving the patient at high-risk for significant infection. This research project will investigate the use of particular pre-transplant conditioning regimen (chemotherapy, antibodies and total body irradiation) followed by a stem cell infusion from a "mismatched" family member donor. Once these stem cells are obtained they will be highly purified in an effort to remove T cells using the investigational CliniMACS stem cell selection device. The primary goal of this study will be to determine the rate of neutrophil and platelet engraftment, as well as the degree and rate of immune reconstitution in the first 100 days posttransplant for patients who receive this study treatment. Researchers will also study ways to decrease complications that may occur with a transplant from a genetically mismatched family donor.