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.

BackgroundPlerixafor 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. Study Design and MethodsWe 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. ResultsDuring 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 7.48x10(6)/L after the first dose. They collected only 0.15x10(6) to 1.63x10(6) (median,0.40x10(6)) CD34+ cells/kg after one to four collections. The median average daily yield was 0.24x10(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 3.04x10(6) to 127.54x10(6)/L (median,14.58x10(6)/L). After one to four doses of plerixafor, each patient collected an additional 0.39x10(6) to 14.02x10(6) (median,1.89x10(6)) CD34+ cells/kg, and the median daily average was 0.78x10(6) CD34+ cells/kg. Cumulatively, after two rounds of collections, 15 collected more than 2.0x10(6) CD34+ cells/kg. Thirteen have proceeded to autologous stem cell transplantation (ASCT) and successfully engrafted. ConclusionIn 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.