Efficacy of pre-emptively used plerixafor in patients mobilizing poorly after chemomobilization: a single centre experience

A significant proportion of patients with lymphoid malignancies are hard-to-mobilize with a combination of chemotherapy plus granulocyte colony-stimulating factor (G-CSF) (chemomobilization). Plerixafor is a novel drug used to improve mobilization of blood stem cells. However, it has been studied mainly in association with G-CSF mobilization. We evaluated the efficacy of 'pre-emptive' use of plerixafor after chemomobilization in patients who seem to mobilize poorly. During a 15 month period, altogether 63 patients with lymphoid malignancies were admitted to our department for blood stem cell collection. Sixteen patients (25%) received plerixafor after the first mobilization due to the low blood (B) CD34+ cell counts (n = 12) or poor yield of the first collection (n = 4). The median number of plerixafor injections was 1 (1-3). The median B-CD34+ count after the first plerixafor dose was 39 x 106/L (< 1-81) with the median increase of fivefold. Stem cell aphaereses were performed in 14/16 patients (88%) receiving plerixafor and a median of 2.9 x 106/kg (1.6-6.1) CD34+ cells were collected with a median of one aphaeresis (1-3). Altogether 13/16 patients mobilized with a combination of chemomobilization and plerixafor received high-dose therapy with stem cell support and all engrafted. Pre-emptive use of plerixafor after chemomobilization is efficient and safe and should be considered in poor mobilizers to avoid collection failure. In patients with low but rising B-CD34+ counts, the use of plerixafor might be delayed as late mobilization may occur. Further studies are needed to optimize patient selection and timing of plerixafor.