Cyclophosphamide Mobilization Does Not Improve Outcome in Patients Receiving Stem Cell Transplantation for Multiple Myeloma

PurposePatients with multiple myeloma who undergo autologous stem cell transplantation (ASCT) and exhibit a complete response (CR) have a superior overall survival and time to progression (TTP). High-dose cyclophosphamide is often used before ASCT for mobilization of hematopoietic stem cells. We hypothesized that cyclophosphamide might further improve CR rates in patients undergoing ASCT. We searched the Mayo Clinic myeloma transplantation database for patients who had stem cell mobilization with hematopoietic growth factor alone or cyclophosphamide and growth factor. The impact of cyclophosphamide on CR rates and TTP was evaluated.Patients and MethodsA cohort of 201 patients was identified: 127 mobilized with cyclophosphamide and growth factor and 74 with growth factor alone. There were no statistically significant differences between the 2 cohorts in regard to age, sex, β2-microglobulin level, plasma cell labeling index, cytogenetics, conditioning regimen, or disease status at time of transplantation.ResultsComplete response rates were 37.4% and 41.3% (P = 0.6115) for patients mobilized with cyclophosphamide combined with growth factor and growth factor alone, respectively, and TTPs were 19.9 months and 20.9 months (P = 0.59). In a multivariate analysis for TTP, cytogenetics and CR rates were the only independent variables (P = 0.0012 and P < 0.0001, respectively).ConclusionWe conclude that high-dose cyclophosphamide does not increase overall CR rates or improve TTP for patients with myeloma undergoing ASCT.