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.
Increase in macrophage progenitor cell number in femoral marrow of mice after continuous infusion or repeated injections of a macrophage colony-stimulating factor.
