increase from 40- to 80-fold after 4-5 days of G-CSF and returns to baseline value within 4-6 days after cessation of G-CSF. Sheridan et al.19 were the first to report that hematopoietic reconstitution can be accomplished after G-CSF-mobilized PBSC following high-dose chemotherapy. The time to platelet and RBC transfusion independence was shorter with G-CSF-mobilized PBSC. Chao et al.20 reported the results of hematopoietic recovery in 85 patients with Hodgkin's disease who received autologous PBSCT using PBSC collected during steady-state or G-CSF-mobilized PBSC, with or without BM. The use of G-CSF-mobilized PBSC resulted in a significantly accelerated time to recovery of granulocytes (10 days vs 12 days; P < 0.01) and platelet engraftment (13 days vs 30 days; P < 0.001).

Two randomized studies have also shown the benefits of G-CSF-mobilized PBSC compared to autologous BM after high-dose therapy. Fifty-eight patients with heavily pretreated Hodgkin's and non-Hodgkin's lymphoma (NHL) were randomized to receive either G-CSF-mobi-lized PBSC or autologous BM.21 All patients received G-CSF after transplant. Patients who received G-CSF-mobi-lized PBSC had faster engraftment of both absolute neutrophit count (ANC) > 0.5 X 109/L (11 days vs 14 days; P = 0.005) and platelet recovery more or equal to 20 X 109/L (16 days vs 23 days; P = 0.02). Similar results were reported by Hartman et al.8 in a larger randomized study of 129 patients with solid tumor and lymphomas. In addition, a cost analysis showed that the total cost was decreased by 17% in adults and 29% in children receiving PBSC transplantation.

The doses of G-CSF used for mobilization are also important and several studies have shown that using higher doses of G-CSF results in a higher number of CD34+, or CFU-GM yield and a lesser number of collections. Nademanee et al.22 showed a dose-response effect for G-CSF, with a sevenfold increase in the number of CD34+ cells in the PB over the baseline value for 5 ^g/kg perday and 28 times for 10 ^g/kg per day. Similarly, there were 10- and 17-fold increases in CFU-GM over baseline for 5^g/kg per day and 10 ^g/kg per day of G-CSF, respectively. Weaver et al.23 conducted randomized studies to evaluate different doses of G-CSF, 10, 20, 30, or 40 ^g/kg per day on yields of CD 34+cells in patients with breast cancer. The median number of CD34+ cells collected after 10 ^g/kg per day was 0.7 X 106/kg per apheresis (range 0.1-4.4) as compared to 1.2 (range 0.1-6.8) after 30 ^g/kg per day (P = 0.04). Patients receiving 10 ^g/kg had lower yields of CD34+ cells and had a 3.3-fold increase in the probability of not achieving more or equal to 5.0 X 106 CD34+ cells per kg as compared to patients receiving 20-40 ^g/kg. These data suggest that doses of G-CSF > 10 ^g/kg per day mobilize more CD34+ cells and may be useful when high numbers of CD34+ cells are desired.

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