CD34+ selected stem cell boosts can improve poor graft function after paediatric allogeneic stem cell transplantation

Poor graft function (PGF) is a severe complication of haematopoietic stem cell transplantation (HSCT) and administration of donor stem cell boosts (SCBs) represents a therapeutic option. We report 50 paediatric patients with PGF who received 61 boosts with CD34(+) selected peripheral blood stem cells (PBSC) after transplantation from matched unrelated (n=25) or mismatched related (n=25) donors. Within 8weeks, a significant increase in median neutrophil counts (0.6 vs. 1.516x10(9)/l, P<0.05) and a decrease in red blood cell and platelet transfusion requirement (median frequencies 1 and 7 vs. 0, P<0.0001 and <0.001), were observed, and 78.8% of patients resolved one or two of their cytopenias. 36.5% had a complete haematological response. Median lymphocyte counts for CD3(+), CD3(+)CD4(+), CD19(+) and CD56(+) increased 8.3-, 14.2-, 22.- and 1.6-fold. The rate of de novo acute graft-versus-host disease (GvHD) grade I-III was only 6% and resolved completely. No GvHD grade IV or chronic GvHD occurred. Patients who responded to SCB displayed a trend toward better overall survival (OS) (P=0.07). Thus, administration of CD34(+) selected SCBs from alternative donors is safe and effective. Further studies are warranted to clarify the impact on immune reconstitution and survival.