Advances in unrelated cord blood transplants in malignancies.

Cord blood is an unlimited source of hematopoietic stem cells (HSCs) for allogeneic HSC transplant. Since the first human cord blood transplant performed 20 years ago, cord blood banks have been established worldwide for collection and cryopreservation of cord blood for allogeneic HSC transplant. More than 500 000 cord blood units are now available for international exchange of cord blood units. A global network of cord blood banks and transplant centers has been established for a common inventory and study of clinical outcomes. Results of unrelated allogeneic cord blood transplants in malignant and nonmalignant diseases, in adults and children, show that, compared with HLA-matched unrelated bone marrow transplant, cord blood has several advantages including prompt availability of the transplant, decrease of graft versus host disease and better long-term immune recovery resulting in a similar long-term survival. Several studies have shown that the number of cells is the most important factor for engraftment while some degree of HLA mismatches is acceptable. Progresses in this field are expected to facilitate engraftment including ex vivo expansion of stem cells, intra-bone injection of cord blood cells and double cord blood transplants.