Preclinical studies have demonstrated the rapid and efficient mobilization of hematopoietic peripheral blood stem cells (PBSC) in a mouse model using the combination of paclitaxel with recombinant human granulocyte colony-stimulating factor (rhG-CSF). On the basis of these results, a clinical trial was initiated using rhG-CSF with paclitaxel for PBSC mobilization in high-risk breast cancer patients. The mobilized PBSC were evaluated for CD34+ cell number, mononuclear cell content, and clonogenic potential. One-hundred and seventeen breast cancer patients received paclitaxel (300 mg/m2) administered as a 24-h continuous intravenous infusion. Forty-eight hours after completing paclitaxel, rhG-CSF (5 μg/kg) was initiated and continued until completion of PBSC collection. Leukapheresis was initiated once the white blood cell count reached 1.0 × 109/L. Each collection was evaluated for the numbers of mononuclear cells (MNC) and CD34+ cells. Clonogenic potential was enumerated using colony-forming units-granulocyte-macrophage (CFU-GM) and burst-forming units-erythroid (BFU-E). Patients receiving paclitaxel with rhG-CSF mobilized a large number of mononuclear cells/apheresis (mean, 3.7 × 108; range, 3.3-4.1) and CD34+ cells/apheresis (mean, 7.2 × 106; range, 6.1-8.4). The average number of leukophereses needed was 1.8 (mean, range 1.6-2.0). Colony growth was normal with 178.9 × 105 and 214.8 × 105 colonies counted in CFU-GM and BFU-E assays, respectively. Patients engrafted platelets and neutrophils on day 10 following transplantation. In conclusion, PBSC mobilization with paclitaxel and rhG-CSF results in a large number of mononuclear cells and CD34+ cells with normal clonogenic potential. The cells engraft normally following high-dose chemotherapy and autologous stem cell transplantation in high-risk breast cancer patients. These results demonstrate that paclitaxel with rhG-CSF is an efficient mobilizing agent in high-risk breast cancer patients.
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