Alternative donors hematopoietic stem cells transplantation for adults with acute myeloid leukemia: Umbilical cord blood or haploidentical donors?

Use of allogeneic transplantation for patients with acute myeloid leukemia (AML) depends mainly on the risk of the disease, and HLA matched donor availability. In patients with high-risk leukemia, in the absence of a HLA (human leukocyte antigen) matched donor, alternative donors such as unrelated umbilical cord blood (UCB) or haploidentical donor (haplo) have been currently used. Both strategies have important advantages such as shorter time to transplant, which is particularly relevant to patients requiring urgent transplantation, and tolerance of HLA mismatched graft that make possible that a donor can be found for virtually all patients. However, in spite of higher incidence of graft failure in UCB transplatation recipients and higher relapse incidence after haplo transplants, final outcomes seem to be comparable with HLA matched unrelated hematopoietic stem cell transplantation (bone marrow or peripheral blood). Therefore, the complexity of choosing the best alternative donor will depend on urgency of the transplantation, status and risk of the disease, donor criteria and center experience. Here we review the current status of UCBT and haplo transplants to treat adults with high-risk acute myeloid leukemia and we discuss the main issues associated with the use of both hematopoietic stem cell transplant approaches.