Should double cord blood transplants be the preferred choice when a sibling donor is unavailable?

Umbilical cord blood transplant is an important alternative stem cell source for both children and adults with haematologic malignancies. Umbilical cord blood units are rapidly available and have less stringent human leucocyte antigen (HLA) matching requirements. Mismatch at two antigens actually improves the risk of relapse for umbilical cord blood transplant recipients with relatively low risk of severe acute or chronic graft-versus-host disease. However, umbilical cord blood transplant is associated with an inferior neutrophil recovery rate when compared with other stem cell sources. Therefore, we have explored double-unit umbilical cord blood transplants, not only as a platform for evaluating the safety and effectiveness of new methods of ex vivo expansion or methods of enhanced homing, but also as an approach in itself to remedy the problem of limited cell dose, particularly for adults.