Hematopoietic Cell Transplantation Using Reduced-Intensity Conditioning Is Successful in Children with Hematologic Cytopenias of Genetic Origin

• Children with severe hematologic cytopenias and bone marrow failure of genetic origin can be cured after related or unrelated donor hematopoietic stem cell transplantation in >80% of recipients.
• Reduced-intensity conditioning using alemtuzumab, fludarabine, and melphalan is sufficient to achieve full donor engraftment in children with bone marrow failure (excluding those with Fanconi anemia, who were not included in this study).
• All survivors were successfully off all immunosuppression and supportive care by 2 years after transplantation.

Genetically derived hematologic cytopenias are a rare heterogeneous group of disorders. Allogeneic hematopoietic cell transplantation (HCT) is curative but offset by organ toxicities from the preparative regimen, graft rejection, graft-versus-host disease (GVHD), or mortality. Because of these possibilities, consideration of HCT can be delayed, especially in the unrelated donor setting. We report a prospective multicenter trial of reduced-intensity conditioning (RIC) with alemtuzumab, fludarabine, and melphalan and HCT in 11 children with marrow failure of genetic origin (excluding Fanconi anemia) using the best available donor source (82% from unrelated donors). The median age at transplantation was 23 months (range, 2 months to 14 years). The median times to neutrophil (>500 × 106/L) and platelet (>50 × 109/L) engraftment were 13 (range, 12 to 24) and 30 (range, 7 to 55) days, respectively. The day +100 probability of grade II to IV acute GVHD and the 1-year probability of limited and extensive GVHD were 9% and 27%, respectively. The probability of 5-year overall and event-free survival was 82%; 9 patients were alive with normal blood counts at last follow-up and all were successfully off systemic immunosuppression. In patients with genetically derived severe hematologic cytopenias, allogeneic HCT with this RIC regimen was successful in achieving a cure. This experience supports consideration of HCT early in such patients even in the absence of suitable related donors.