The impact of the CD34+ cell dose on engraftment in allogeneic peripheral blood stem cell transplantation

Forty-five patients who underwent allogeneic peripheral blood stem cell transplantation (PBSCT) were evaluated in order to investigate any relationship between CD34+ cell dose given and hematological recovery. Granulocyte counts >1.0 × 10⁹/L and platelet >50 × 10⁹/L were considered as hematological recovery. Three different regimens were used for mobilization, by adjusting the recombinant granulocyte colony stimulating factor (rhG-CSF, Roche) dose. The first group (n=3), whose donors mobilized with 5 μg/kg/d s.c. rhG-CSF received a mean of 5.9 × 10⁶/kg (95% confidence interval for mean (CI); 2.4–9.3) CD34+ cells. The second group (n=37), mobilized with 10 μg/kg/d s.c. rhG-CSF and the third group (n=5) mobilized with 15 μg/kg/d s.c. rhG-CSF, received a mean of 5.7 × 10⁶/kg (95% CI; 4.6–6.75) and 6.56 × 10⁶/kg (95% CI; 4.57–8.55) CD34+ cells, respectively. CD34+ cell dose was 5.82 × 10⁶/kg (95%CI; 4.97–6.68) for all the patients. All patients received rhG-CSF from day +1 until attaining granulocyte count >1.0 × 10⁹/L for three consecutive days. Median granulocyte and platelet engraftment days for the whole group was 15 (range; 11–44) and 14 (11–54) days respectively. There was a close correlation (r=−0.301, p < 0.05) between the CD34+ cell dose and granulocyte recovery for the whole group. When these analyses were performed separately within groups, this correlation was also found significant for the first group (r=−0.99, p < 0.05) for granulocyte recovery. On the contrary the same analysis did not reach significance for the other groups, nor for platelet recovery for the whole group (r=0.039, p=0.821). We calculated a minimum dose of 4 × 10⁶/kg CD34+ cells for a safe alloPBSCT. There was no difference between patients who received more than 5 × 10⁶/kg CD34+ cells, and those who received more than 2 × 10⁶/kg and less than 5 × 10⁶/kg CD34+ cells. In conclusion, we have demonstrated a correlation between the CD34+ cell dose given and faster hematological recovery for alloPBSCT patients.