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 8 weeks, a significant increase in median neutrophil counts (0·6 vs. 1·516 × 109 /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.