Kinetics of blood CD34(+) cells after chemotherapy plus G-CSF in poor mobilizers: implications for pre-emptive plerixafor use.

Mobilization and collection of stem cells is difficult in a proportion of patients intended for autologous stem cell transplantation (ASCT). We have evaluated mobilization kinetics of blood CD34(+) cells (B-CD34(+)) to form basis for algorithm to facilitate rational pre-emptive plerixafor use. Altogether 390 chemomobilized patients were included.Forty-three patients (11%) did not reach BCD34+count ≥10×10(6)/l. Mobilization kinetics differed according to the mobilization capacity observed. Among those who were very poor or inadequate mobilizers (peak BCD34(+)count ≤5×10(6)/l and 6–10×10(6)/l, respectively), BCD34+counts rarely rose after white blood cells (WBC) >5–10×10(9)/l, whereas in many standard mobilizers a later rise in CD34(+) counts could be observed. Four algorithms based on WBC and CD34(+) counts were constructed. According to this patient series, algorithm II (WBC >5×109/l and BCD34+≤10×10(6)/l) and algorithm IV (WBC >10×10(9)/l andB-CD34(+) ≤10×10(9)/l) were the most applicable. For algorithm II the sensitivity was 0.97 and specificity 1.00, respectively, to identify patients for plerixafor use provided that all patients with B-CD34+ maximum ≤10×10(6)/l would have needed plerixafor.This simple model needs a prospective validation.