Can the bone marrow harvest volume be reduced safely in hematopoietic stem cell transplantation with pediatric sibling donors?

Background Reduced harvest volumes in pediatric donors appear to have the potential to reduce donor-associated risks while maintaining engraftment in recipients; however, the allowable harvest volume reduction remains undefined. Methods We retrospectively analyzed the data pairs of 553 bone marrow (BM) harvests from pediatric (age at harvest ＜18 yr) sibling donors and clinical outcomes of 553 pediatric (age at infusion ＜14 yr) transplant-naïve recipients to assess the optimal BM harvest volume needed from pediatric donors to obtain the desired CD34+ cell count (≥3.0×106 cells per kg of recipient weight), and to study its impact on the clinical outcomes of transplantation in pediatric recipients. Results The minimum desired CD34+ cell count of ≥3.0×106 per kg of recipient weight was achieved for 506 (95.3%) of donor-recipient pairs. The median CD34+ cell yield was 6.4×106 per kg of recipient weight (range, 1.2‒33.8×106) in donors younger than 5 years old at harvest, 4.7×106 (range, 0.3‒28.5×106) in donors aged 5‒10 years and 2.1×106 (range, 0.3‒11.3×106) in donors older than 10 years (P＜0.001). Conclusion The infused CD34+ cell dose (×106 cells/kg of recipient weight) had no impact on GRFS; however, a CD34+ cell dose of ＞7×106 cells/kg of recipient weight did not improve hematopoietic recovery.