Blood, Prepublished online December 9, 2012; doi:10.1182/blood-2012-08-449108, Scaradavou A et al
Cell dose is a major limitation for umbilical cord blood (UCB) transplantation since units containing a minimum of 2.5 x 107 total nucleated cells (TNC)/ kilogram patient body weight are frequently not available. The transplantation of two partially HLA-matched UCB units has been adopted as a simple approach for increasing the TNC. We sought to determine whether the relative safety and efficacy of this approach was comparable to a single UCB transplant. Included are adults with acute leukemia transplanted with one (n=106) or two UCB units (n=303). All UCB units for single UCB transplants contained TNC ≥2.5 x 107/kg. For double UCB transplants, the total TNC for units 1 and 2 were greater than 2.5 x 107/kg but in about half of these transplants, one of the two units contained <2.5 x 107 TNC/kg. Adjusting for factors associated with outcomes, risks of neutrophil recovery (OR 0.83, p=0.59), transplant-related mortality (HR 0.91, p=0.63), relapse (HR 0.90, p=0.64) and overall mortality (HR 0.93, p=0.62) was similar after double UCB and adequate dose single UCB transplants. These data support double UCB unit transplantation for acute leukemia when an adequately dosed single UCB unit is not available thereby extending access to nearly all patients.