Long‐Term Hematopoietic Engraftment after Autologous Peripheral Blood Progenitor Cell Transplantation in Pediatric Patients: Effect of the CD34+ Cell Dose

Background and Objectives: We analyzed the relationship between long‐term hematopoietic recovery and the number of CD34+ cells infused in order to determine the optimal dose of CD34+ cells for rapid and stable engraftment. Patients and Methods: Between November 1993 and December 1998, 96 consecutive autologous transplantations were performed in 92 pediatric patients with different malignancies. Peripheral blood progenitor cells (PBPC) were mobilized by G‐CSF alone (12 μg/kg/day s.c., Neupogen®, Amgen, Thousand Oaks, Calif., USA) and collected using a Cobe Spectra blood cell separator (Cobe, Denver, Colo., USA) through a central venous catheter with double lumen. The CD34+ cell contents of apheresis products were assessed by means of flowcytometric analysis using an Epics Elite flow cytometer (Coulter, USA). Results: The median number of CD34+ cells infused was 3.2 × 106/kg (range 0.17‐44.4). The median times for short‐term engraftment (neutrophil count >0.5 × 109/1 and platelet count >20 × 109/1) was 9 (range: 7–16) and 13 days (range: 7–91), respectively. The median times for long‐term engraftment (platelet count>50 × 109/1 and >100 × 109/1) was 21 (range: 10–249) and 45 days (range: 12–288). When the infused CD34+ cell dose was ≥5 × 106/kg (median 7.99, range 5.01–44.4), there was a statistically significant increase in the rate of short‐ and long‐term hematopoietic recovery compared to patients transplanted with a lower number of CD34+ cells (p < 0.0001). The earlier recovery in the high CD34+ cell group resulted in less transfusional support, fewer days on intravenous antibiotics and shorter hospitalization. Conclusions: This study confirms that G‐CSF‐mobilized PBPC provide rapid short‐and long‐term hematopoietic engraftment in pediatric patients undergoing autologous transplantation if a CD34+ cell dose ≥5.0 × 106/kg is infused. As this PBPC dose seems to have clinical and potentially economic implications, it should be considered the optimal dose for apheresis.