Trial Of Double Umbilical Cord Blood Transplantation

This pilot research study is to investigate the safety and effectiveness of stem cell transplantation to treat blood-related (hematopoietic) cancers, using stem cells collected from two different, umbilical cord blood donors. Subjects in this study are receiving a stem cell transplant because other treatments have failed or their disease is unlikely to respond to other treatment options. Blood-related cancers can be treated and sometimes cured with very high doses of chemotherapy and radiation therapy, given to kill the cancer cells; however, these treatments can prove unsuccessful and can harm normal cells in the bone marrow or a patient's disease may be unlikely to respond to these treatment options. Hematopoietic stem cells transplantation (HSCT) is a potential cure, but opportunities to perform HSCT are limited by donor availability. Only 20-30% of patients may have matched family donors. In some cases, a mismatched family donor may be suitable. For patients needing a transplant who do not have a suitably matched family donor, blood stem cells from matched unrelated donors can be used. The length of time required to identify a matched unrelated donor presents another obstacle for patients waiting to receive an HSCT. Blood stem cells are found in umbilical cord blood (UCB), which is blood left over in the placenta (afterbirth) after a baby is born. Usually this blood is discarded with the placenta, but over the past 15 years, we have learned how to collect and freeze cord blood cells to be used for transplants at a later time. A cord blood unit is the cord blood cells collected and stored from a single placenta. More than 6,500 umbilical cord blood stem cell transplants have been done worldwide, mostly in children with leukemia. One important factor affecting the success of a cord blood transplant is the cell dose (number of stem cells in the cord blood unit / recipient's weight). Patients who receive a high cell dose (\> 2.5 x 107 cells/kilogram) have better