Post-Thaw Viable CD45+ Cells and Clonogenic Efficiency are Associated with Better Engraftment and Outcomes after Single Cord Blood Transplantation in Adult Patients with Malignant Diseases

• We studied the role of quantity and quality variables tested at time of infusion of hematopoietic progenitor cells from cord blood used for the treatment of malignant diseases
• We analyzed the impact on outcomes after transplantation of quantity and quality variables of cord blood stem cell progenitors
• We report that only 2 quality variables (viable CD45+ and estimated clonogenic efficiency) influence the results of cord blood transplantation
• The latter 2 quality variables have not been reported before as prognostic factors after cord blood transplantation
• Determining viable CD45+ and estimated clonogenic efficiency on contiguous segment to the bag may help with selection of cord blood units for transplantation and with avoiding use of cord blood units with impaired function

The quantity of cells is widely accepted as the main factor influencing the outcome after umbilical cord blood transplantation (UCBT) however, the quality of the cord blood units (CBUs) has been less studied. In order to determine the impact of qualitative variables in UCBT outcomes, we conducted a multicenter retrospective study in adult patients with hematological malignancies who underwent single UCBT after a common myeloablative conditioning regimen. One hundred and ten patients from 3 institutions [median age, 35 years (range 18-55)] were included. Quantitative (TNC and total CD34+cells) and qualitative variables [viable CD45+ (vCD45+), vCD34+ and clonogenic efficiency [(CLONE), quotient of post-thaw colony-forming units (CFU)] and pre-freeze CD34+ cells predicted engraftment in univariate analysis however, only 2 qualitative variables remained significant in the multivariate analysis. Infusion of more than 2 × 107 post-thaw vCD45+ cells per kilogram was significantly associated with faster neutrophil (P = .01), platelet engraftment (P = .01), higher disease-free (P = .01) and overall survival (0.02). In addition, CLONE ≥ 20% predicted a faster neutrophil (P = .005), platelet engraftment (P = .01) and contributed to decrease the non-relapse mortality (P = .02). Our study suggests that the vCD45+ cells dose and CLONE are powerful surrogate markers of graft quality and can potentially help on CBUs selection if tested with representative reference samples.