[Mobilization of peripheral blood stem cells with conventional chemotherapy]

Autologous peripheral blood progenitor cells (PBPC) rescue after high-dose chemotherapy has been used progressively as a form of treatment in some solid and hematologic tumors. This increasing use can be explained by both advantages of PBPC rescue over bone marrow rescue (decrease in the duration of marrow aplasia, reduction of platelet transfusions, earlier discharge from hospital, potential use in patients with inadequate bone marrow reserve) and the low number of aphereses (one or two) needed to collect a sufficient number of progenitor cells for autografting. High-dose chemotherapy is likely to be increasingly used after the results of two recently reported studies in which treatment with high-dose compared with standard-dose chemotherapy increases overall survival in metastatic breast cancer patients and relapsed lymphoma patients. After the initial use of unselected mobilizing regimens regardless of the patient characteristics and the tumor type, now it seems more useful to optimize this approach. Mobilization of PBPC can be obtained by several approaches. Moderate or high doses of single agent alone (e.g. cyclophosphamide 4-7 g/m2) or some hematopoietic growth factors alone (e.g. G-CSF, GM-CSF) have been proven to be adequate mobilizing agents. However, the use of hematopoietic growth factors alone may disadvantageously delay the start of an effective chemotherapy. An efficient mobilizing regimen requires the use of both chemotherapy and hematopoietic growth factors: the efficiency of mobilization was greater and with less side effects than chemotherapy alone. It was postulated that PBPC mobilization could be achieved only at hematopoietic recovery following myeloablative chemotherapy. Recently, it has been demonstrated that some standard-dose chemotherapy regimens associated with hematopoietic growth factors are efficient priming agents. We reported that standard-dose CEF chemotherapy plus filgrastim is a disease specific regimen (breast cancer) allowing PBPC mobilization without any relevant toxicity. The maximum release of PBPC has been observed at day 11. The optimal time for PBPC collection is predictable and aphereses can be guided by WBC counts. In conclusion, both standard and high dose chemotherapy are effective priming regimens. So presently a mobilizing regimen should be an effective disease specific chemotherapy program and should contain a hematopoletic growth factor. The choice between standard and high-dose chemotherapy can be based on patients characteristic and disease status.