Comparison of pre-cryopreserved and post-thaw-and-wash-nucleated cell count on major outcomes following unrelated cord blood transplant in children.

Engraftment and OS after umbilical CBT is highly dependent on the TNC. The contribution of the wash step to cell loss and ultimately the dose of cells available for transplant is not well described. To investigate the amount of cell loss after washing and its impact on major outcomes compared to pre-cryopreserved TNC, we analyzed data from patients prospectively enrolled on a National Heart, Lung and Blood Institute sponsored cord blood transplant study between 1999 and 2003. There were 310 patients ≤18 yr of age with malignant (N = 218) or non-malignant (N = 92) disease enrolled on this trial. Only single CBU were used. All CBU were thawed and washed using an identical process. The median TNC after thawing and washing (PTW) was 5.43 × 10(7) /kg (79% recovery of cells). The cumulative incidence of neutrophil engraftment was significantly higher in patients receiving a PTW TNC ≥2.5 × 10(7) /kg (p = 0.01). The cumulative incidence of TRM was higher among patients receiving post-thaw-and-wash TNC <2.5 × 10(7) /kg (p = 0.039). In conclusion, receiving a PTW TNC of <2.5 × 10(7) /kg resulted in worse neutrophil engraftment and increased transplant-related mortality compared to a PTW TNC of ≥2.5 × 10(7) /kg.