Successful hematopoietic stem cell collection in patients who fail initial plerixafor mobilization for autologous stem cell transplant

We report our experience of collecting stem cells in patients who failed to mobilize sufficient hematopoietic stem cell (HSC) using plerixafor (P) in the initial mobilization attempt. Twenty four patients were identified who failed a first mobilization attempt using P. Of these, 22 patients received granulocyte colony stimulating factor (G-CSF) and two patients received cyclophosphamide (CY)1G-CSF in combination with P for the initial attempt. The agents used for second collection attempt were granulocyte macrophage colony stimulating factor (GM-CSF)1G-CSF (19 patients), G-CSF1P (three patients), CY1G-CSF (one patient), and bone marrow harvest (one patient). A median of 0.6 × 10⁶ CD₃₄⁺ cells/kg (range 0-1.97) were collected in the initial attempt. A second collection was attempted at a median of 22 days (range 15-127) after the first failed mobilization. The median CD₃₄⁺ cell dose collected with the second attempt was 1.1 × 10⁶ CD₃₄+ cells/kg (range 0-7.2). A third collection was attempted in six patients at median of 51 days (range 34-163) after the first failed mobilization. These patients collected a median of 1.1 × 10⁶ CD₃₄1 cells/kg (range 0-6.5). Total of 16 patients (67%) collected sufficient cells to undergo autologous stem cell transplant and eight patients (33%) were able to collect ≥2 × 10⁶ CD₃₄+ cells/kg in a single subsequent attempt. Our experience suggests that a majority of patients who fail primary mobilization despite use of P can collect sufficient HSC with a subsequent attempt using combination of G-CSF with either P or GM-CSF.