Double cord blood transplantation: extending the use of unrelated umbilical cord blood cells for patients with hematological diseases.

Unrelated umbilical cord blood (UCB) has been widely used to treat patients lacking a well-matched HLA donor. Cell dose is a critical determinant of outcomes in cord blood transplantation, limiting the use of this strategy for low body weight patients. To overcome this limitation, infusion of two partially HLA-matched cord units was adopted as a new strategy. Since 2005, number of adult patients treated with UCB transplant is increased due to the higher number of cells available using two units and to the feasibility of reduced intensity conditioning regimen, extending successfully this strategy to heavier patients or for those with co-morbidities. Approximately 993 adults with hematological diseases have been transplanted with double UCB graft, and reported to Eurocord registry from 1999 to 2010. This article reviews the state of art and future directions with double umbilical cord blood units as a source of hematopoietic stem cells for transplantation.