A simplified approach to stem cell mobilization in multiple myeloma patients not previously treated with alkylating agents

High-dose chemotherapy and autologous stem cell rescue is considered a standard part of initial therapy for patients with multiple myeloma. Therefore, potential transplant candidates are generally treated with dexamethasone-based programs rather than alkylating agents to avoid stem cell toxicity. The optimal mobilizing regimen for patients with multiple myeloma has not been defined. However, aggressive chemotherapy may result in excessive morbidity and cost in this older, immunocompromised population. We retrospectively examined our experience with a well-tolerated regimen of 1.5 g/m² cyclophosphamide on day -10 followed by 10 μg/kg G-CSF beginning on day -7 in 50 consecutive patients with multiple myeloma and no prior alkylating agent therapy. Median stem cell collection was 4.88 × 10⁶ CD34+ cells/kg per apheresis and 44 patients collected >5 × 10⁶ CD34+ cells/kg within 2 days. In 36 patients, more than 10 × 10⁶ CD34+ cells/kg were collected including 33 patients who required 1-2 days of collection. One patient required hospitalization for fever/neutropenia and two required weekend apheresis. We conclude that 1.5 g/m² cyclophosphamide plus 10 μg/kg G-CSF is a safe, effective, highly predictable mobilizing program that uniformly provided enough stem cells for one transplant and enough stem cells for two transplants.