Factors Predicting PBPC Collections in Healthy Adolescents and Children with Solid Tumours.

G-CSF is used for mobilization of hematopoietic cells in healthy adolescent donors and pediatric patients. In both groups it is important to ascertain factors predicting the success of apheresis as well as the number of procedures to achieve the target CD34+ cell number for hematologic recovery. We retrospectively analyzed factors predicting the yield for a target CD34+ cell dose in10 healthy adolescent donors and 43 children with solid tumours who were enrolled in the transplantation program at our center from January 1996 to July 2007. The healthy adolescents (n=10) had a median age of 15 years (range 13–16) and body weight (bw) of 45 kg (range 20–74) and the children with solid tumours (n=42) (Neuroblastoma n=28, Ewing sarcoma n=7 and other solid tumours n=7) had a median age of 4 years (range 1–15) and bw of 17 kg (range 9 – 63). Mobilization regimen consisted of G-CSF in a dosage of 10 μg/kg per day, applied subcutaneously for 5 or 6 days. A pre-collection peripheral blood (PB) CD34+ count was performed in all children, by flow cytometric analysis. Standard volume apheresis was carried out using a Cobe Spectra blood cell separator, through peripheral veins in donors and central lines in patients. We estimated a minimum of 4 x10⁶ and 2x10⁶ CD34+ cells/kg bw receptor for successful engraftment for allogeneic and autologous transplant, respectively. The healthy adolescent donors had high number of PB CD34+ cells (median 62/μl, range 42 – 75) and the majority (7/10) only required a single apheresis to collect sufficient cells for their family related recipients. The neuroblastoma patients with >10/μl PB CD34+ cells collected in one day the target cell dose (median 4.6x10⁶ CD34+ cells/kg, range 2.6 – 27.0). Those with <10/μl PB CD34+ cells underwent 2 apheresis and the majority reached the cell target. The majority of children with Ewing sarcoma and other solid tumours (9/14) also collected >2.0 x10⁶ CD34+ cells/kg in 2 apheresis. In summary all the children with solid tumours received a single course of G-CSF and presented on the 5^th day of mobilization a median PB CD34+ cell count of 9/μl (range 1–216). The majority (75%) collected >2.0 x10⁶ CD34+ cells/kg and the remaining (25%) had <10/μl PB CD34+ cells and did not achieve this minimum requirement. We found a correlation between the PB CD34+cell count and the number of apheresis and CD34+ cells yielded both for the adolescent donors and children with solid tumours. Based on these results, a PB CD34+ cell count >10/μl was a good indicator for performing PBPC collections in paediatric patients from our institution.