Comparison of engraftment following different stem cell mobilization modalities in patients with multiple myeloma treated with a uniform induction regimen containing bortezomib, cyclophosphamide and dexamethasone.

Bortezomib-based induction followed by autologous stem cell transplantation is a common treatment for multiple myeloma (MM). Stem cell (SC) mobilization with granulocyte-colony stimulating factor (G-CSF) alone has become an alternative to G-CSF combined with chemotherapeutic agents. This study aimed to compare the efficacy of the two mobilization modalities following induction with a uniform regimen containing bortezomib, cyclophosphamide and dexamethasone (VCD). We retrospectively evaluated results of SC mobilization using either G-CSF alone or combined with high-dose cyclophosphamide (HD-CY) in MM patients after VCD induction. The primary endpoints of the study were engraftment and mobilization-associated toxicity. Parameters of stem cell collection, transplantation and engraftment were assessed. Data of 92 patients were analyzed [56 (61%) mobilized with HD-CY + G-CSF and 36 (39%) with G-CSF only]. HD-CY + G-CSF provided a higher number of CD34 + cells (15.9 vs 8.1 × 106/kg, p = 0.001) with fewer apheresis sessions. However, while no adverse events were observed in patients receiving G-CSF alone, nine patients (16%) receiving HD-CY + G-CSF developed neutropenic fever requiring hospitalization. Although a greater number of cells was transplanted following mobilization with HD-CY + G-CSF, neutrophil and platelet engraftment and duration of transplant-related hospitalization were similar in both cohorts. G-CSF alone provided a sufficient SC amount, without exposing patients to additional toxicity. While HD-CY + G-CSF resulted in a superior SC yield in MM patients induced with VCD, this advantage should be balanced against adverse effects of this mobilization regimen.