Second time a charm? Remobilization of peripheral blood stem cells with plerixafor in patients who previously mobilized poorly despite using plerixafor as a salvage agent.

Background: Plerixafor is a recently introduced agent used to improve peripheral blood stem cell (PBSC) mobilization in patients with hematologic malignancies. However, some patients still cannot mobilize adequately even with plerixafor.

Methods: We retrospectively reviewed the PBSC collections of 18 consecutive lymphoma and multiple myeloma patients, who had previously mobilized poorly despite the use of plerixafor and received plerixafor again during remobilization.

Results: During the first mobilization attempt, all 18 recombinant granulocyte-colony-stimulating factor (G-CSF; two) or G-CSF plus chemotherapy-mobilized patients (16) had poor response to plerixafor, with peripheral blood (PB) CD34+ counts ranging from 0 to 7.48 × 10(6)/L after the first dose. They collected only 0.15 × 10(6) to 1.63 × 10(6) (median, 0.40 × 10(6)) CD34+ cells/kg after one to four collections. The median average daily yield was 0.24 × 10(6) CD34+ cells/kg. Remobilization began 1 to 4 weeks later with G-CSF, plerixafor, and with (three) or without (15) cyclophosphamide. The PB CD34+ cell counts after the first dose of plerixafor were 3.04 × 10(6) to 127.54 × 10(6)/L (median, 14.58 × 10(6)/L). After one to four doses of plerixafor, each patient collected an additional 0.39 × 10(6) to 14.02 × 10(6) (median, 1.89 × 10(6)) CD34+ cells/kg, and the median daily average was 0.78 × 10(6) CD34+ cells/kg. Cumulatively, after two rounds of collections, 15 collected more than 2.0 × 10(6) CD34+ cells/kg. Thirteen have proceeded to autologous stem cell transplantation (ASCT) and successfully engrafted.

Conclusions: In patients who had responded poorly to the use of plerixafor as a mobilization salvage agent, response to remobilization with plerixafor for the second time was variable, but most (83.3%) patients were able to collect enough PBSCs to proceed to ASCT.