A Phase II Study of Umbilical Cord Blood Transplantation Following Myeloablative or Reduced-Intensity Conditioning

Allogeneic stem cell transplantation (SCT) following myeloablative and non-myeloablative conditioning therapy has proven curative treatment for a number of inherited and acquired hematologic disorders. The success of allogeneic transplantation is largely determined by compatibility between donor and recipient, which predicts the risk of fatal graft-versus-host disease (GVHD). Unfortunately, less than one third of patients needing an allogeneic transplant have an available compatible donor in their family. Registries have been established to match patients with compatible volunteer (unrelated) donors, but many patients, and in particular minority patients, still lack stem cell donors.

Umbilical cord blood (UCB) is a rich source of hematopoietic stem cells, which is readily available from the placenta following childbirth. Blood banks have been established in the United States and abroad to collect, process and store UCB for use in allogeneic transplantation. To date, more than 2000 UCB transplants have been performed in adults and children around the world.

Rationale for use of Umbilical Cord Blood in Transplantation

UCB has a number of proven and theoretical advantages as an alternative source of hematopoietic stem cells for transplantation:

1. Placental or umbilical cord blood is an abundantly available source of stem cells, which is currently discarded and can be harvested at no risk to the mother or infant.
2. Important infectious agents, particularly CMV, are much less common in the newborn than adults, and are less likely to contaminate UCB collections.
3. UCB collections, typed, cryopreserved and banked, are available on demand, eliminating delays and uncertainties that now complicate marrow collection from unrelated donors. At present, UCB can be delivered for infusion within days of the initiation of a search. This compares with a median of 3 months from search to delivery of stem cells through the registries of volunteer adult donors.
4. The intensity of graft-versus-host reactivity of fetal lymphocytes appears to be less than that of adult cells and consequently fetal lymphocytes are more tolerant of HLA incompatibility. Published studies have shown that transplantation of UCB matched at 4-5/6 antigens results in a comparable incidence of GVHD to transplantation of unrelated stem cells fully matched at 6/6 antigens.
5. Frozen UCB can be easily shipped, stored at the treating institution, and thawed for use when needed, compared to freshly donated stem cells which have a limited shelf-life of one day or less, necessitating coordination between harvesting surgeons, transportation, and transplantation teams.