Broad inter-individual variations in circulating progenitor cell numbers induced by granulocyte colony-stimulating factor therapy.

The elevated white cell counts (WCC) and myeloid progenitor cell levels in the blood induced by granulocyte colony-stimulating factor (G-CSF) treatment were studied in three settings: cancer patients previously treated with chemo/radiotherapy (n = 13), untreated cancer patients (n = 5) and normal volunteers (n = 9). The inter-individual variations in progenitor cell mobilization responses to G-CSF and the impact of previous chemo/radiotherapy were investigated. The absolute levels of circulating progenitor cells, but not total white cells, were reduced significantly in the pretreated cancer patients (median 961, range 289-3355 per ml blood) as compared to untreated cancer patients (median 9891, range 2219-16625 per ml blood). In each setting, wide ranges of circulating progenitor cell numbers were observed, and the variation in progenitor cell numbers was considerably greater than observed for the WCC. However, progenitor cell numbers in normal volunteers (942-25296 per ml blood) demonstrated as much variance as observed in pretreated cancer patients. This broad physiological variation in progenitor cell levels induced by G-CSF needs to be considered when designing strategies for allogeneic peripheral blood stem cell transplantation.