Comparison of Peripheral Blood Stem Cell Mobilization with Etoposide or Cyclophosphamide in Patients with Multiple Myeloma

For successful autologous stem cell transplantation, collection of the sufficient number of hematopoietic stem cells is essential after induction therapy for transplant candidates in multiple myeloma (MM). In this study, we compared the efficacy and safety of stem cell mobilization with etoposide (VP-16; 375 mg/m² on days 1 and 2) or cyclophosphamide (CY; 3.0 g/m² on day 1) in patients with MM. Granulocyte-colony stimulating factor (G-CSF, 10 mg/kg/day, subcutaneously) was administered from the development of neutropenia to the final collecting day. Mobilization failure was defined as total collected CD34⁺ cell count < 4.0 x 10⁶ cells/kg in three apheresis procedures. Seventy-six patients were mobilized with CY and G-CSF, and 46 patients were mobilized with VP-16 and G-CSF between February 2008 and July 2017. Median total collected number of CD34⁺ cells was significantly higher in patients who were mobilized with VP-16 compared with those who were mobilized with CY (27.6 x 10⁶ cells/kg vs. 9.5 x 10⁶ cells/kg, P < 0.001). In addition, the rate of mobilization failure was significantly lower in VP-16 group compared with CY group (2.2% vs. 23.7%, HR 0.072, 95% CI 0.009-0.557, P = 0.001). One patients who were mobilized with VP-16 showed mobilization failure and did not achieve the sufficient collection of stem cells in subsequent mobilization process with plerixafor. Severe infections during mobilization period were frequently developed in CY group (15.8% in CY group vs. 8.6% in VP-16 group, P = 0.407). The median time to platelet engraftment (> 20 × 10⁹/L) and neutrophil recovery (> 0.5 × 10⁹/L) did not different between two group after autologous transplantation. In conclusion, VP-16 and G-CSF was a very effective and safe method for peripheral blood stem cell mobilization and is considered as a more suitable chemo-mobilization regimen compared to CY and G-CSF in patients with MM.