Hematopoietic stem cell mobilization with intravenous melphalan and G-CSF in patients with chemoresponsive multiple myeloma: report of a phase II trial

Multiple myeloma ( MM) is an incurable hematologic malignancy for which autologous hematopoietic stem cell transplantation ( HCT) is a standard therapy. The optimal method of stem cell mobilization is not defined. We evaluated intravenous melphalan ( 60 mg/ m(2)), the most effective agent for MM, and G- CSF ( 10 mug/ kg/ day) for mobilization. End points were safety, adequacy of CD34+ collections, MM response, and contamination of stem cell components ( SCC). In total, 32 patients were mobilized. There were no deaths or significant bleeding episodes; 14 patients ( 44%) required hospitalization for neutropenic fever. Median days of grade 3 or 4 neutropenia or thrombocytopenia were 7 ( 2 - 20) and 8 ( 3 - 17). Median mobilization days, CD34+ cells/ kg and total leukaphereses were 16 ( 12 - 30), 12.1 million ( 2.6 - 52.8), and 2 ( 1 - 5) respectively. Four patients ( 12.5 %) failed to achieve the target of 4 million CD34+ cells/ kg in five leukaphereses. Reduction in myeloma was seen in 11 patients ( 34%) wit h 3 ( 9%) achieving complete response; 15 ( 47%) maintained prior responses. Estimated MM contamination per SCC ( N = 48) was 0.0009% ( range 0 - 0.1) and 0.21 x 10 4 cells per kg ( range 0 - 41.2). Increased contamination was associated with increased patient age. This strategy for mobilization is feasible, frequently requires hospitalization and transfusion, and controls disease in most patients.