Randomized Cross-Over Trial of Progenitor-Cell Mobilization: High-Dose Cyclophosphamide Plus Granulocyte Colony-Stimulating Factor (G-CSF) Versus Granulocyte-Macrophage Colony-Stimulating Factor Plus G-CSF

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Abstract
PURPOSE: Patient response to hematopoietic progenitor-cell mobilizing regimens seems to vary considerably, making comparison between regimens difficult. To eliminate this inter-patient variability, we designed a cross-over trial and prospectively compared the number of progenitors mobilized into blood after granulocyte-macrophage colony-stimulating factor (GM-CSF) days 1 to 12 plus granulocyte colony-stimulating factor (G-CSF) days 7 to 12 (regimen G) with the number of progenitors after cyclophosphamide plus G-CSF days 3 to 14 (regimen C) in the same patient. PATIENTS AND METHODS: Twenty-nine patients were randomized to receive either regimen G or C first (G1 and C1, respectively) and underwent two leukaphereses. After a washout period, patients were then crossed over to the alternate regimen (C2 and G2, respectively) and underwent two additional leukaphereses. The hematopoietic progenitor-cell content of each collection was determined. In addition, toxicity and charges were tracked. RESULTS: Regimen C (n = 50) resulted in mobilization of more CD34+ cells (2.7-fold/kg/apheresis), erythroid burst-forming units (1.8-fold/kg/apheresis), and colony-forming units–granulocyte-macrophage (2.2-fold/kg/apheresis) compared with regimen G given to the same patients (n = 46; paired t test, P < .01 for all comparisons). Compared with regimen G, regimen C resulted in better mobilization, whether it was given first (P = .025) or second (P = .02). The ability to achieve a target collection of ≥ 2 × 106 CD34+ cells/kg using two leukaphereses was 50% after G1 and 90% after C1. Three of the seven patients in whom mobilization was poor after G1 had ≥ 2 × 106 CD34+ cells/kg with two leukaphereses after C2. In contrast, when regimen G was given second (G2), seven out of 10 patients failed to achieve the target CD34+ cell dose despite adequate collections after C1. Thirty percent of the patients (nine of 29) given regimen C were admitted to the hospital because of neutropenic fever for a median duration of 4 days (range, 2 to 10 days). The higher cost of regimen C was balanced by higher CD34+ cell yield, resulting in equivalent charges based on cost per CD34+ cell collected. CONCLUSION: We report the first clinical trial that used a cross-over design showing that high-dose cyclophosphamide plus G-CSF results in mobilization of more progenitors then GM-CSF plus G-CSF when tested in the same patient regardless of sequence of administration, although the regimen is associated with greater morbidity. Patients who fail to achieve adequate mobilization after regimen G can be treated with regimen C as an effective salvage regimen, whereas patients who fail regimen C are unlikely to benefit from subsequent treatment with regimen G. The cross-over design allowed detection of significant differences between regimens in a small cohort of patients and should be considered in design of future comparisons of mobilization regimens.

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