Relevance of peripheral blood progenitor cell counts during steady-state hematopoiesis to estimate the number of progenitor cells mobilized followinggranulocyte colony-stimulating factor-supported chemotherapy

Background: Peripheral blood progenitor cells can be mobilized using cytoto xic chemotherapy and cytokines. We were looking for predictive parameters i ndicating a patient's response to a given mobilization regimen. Patients an d Methods: Flow cytometry analysis and clonogrenic assays were used to exam ine hematopoietic progenitor cells in bone marrow and peripheral blood prio r to G-CSF-supported chemotherapy and were compared to CD34+ cell counts in peripheral blood and leukapheresis products in the recovery phase. Stroma- dependent long-term cultures were performed from steady-state bone marrow a nd leukapheresis product samples. 90 patients (24 non-Hodgkin's lymphoma, 5 Hodgkin's disease, 33 multiple myeloma, 28 solid tumor) were included in t his study. Results: A correlation analysis revealed steady-state peripheral blood CD34+ cells tall patients: r = 0.59, p < 0.0001; non-Hodgkin's lymph oma, r = 0.7, p = 0.0003; multiple myeloma: r = 0.71, p < 0.0001) and perip heral blood colony-forming cells but not their bone marrow counterparts to be a measure of a patient's mobilizable CD34+ cell number which may reflect different degrees of blood dilution in the bone marrow aspirates. The prol iferative potential of primitive stem cell clones in the CD34+ population w as comparable between steady-state bone marrow and mobilized peripheral blo od cells. An increasing number of chemotherapy cycles prior to mobilization lead to a depletion of CD34+ cells from steady-state peripheral blood (p = 0.001), mobilized peripheral blood (p = 0.0001), or the mean leukapheresis product CD34+ cell yield (p = 0.0021). Steady-state peripheral blood CD34 cell counts could be related to the individual progenitor cell yields. In order to obtain in one leukapheresis product 2.5 x 10(6) CD34+ cells/kg bod y weight, a steady-state peripheral blood CD34+ cell count of 0.6 x 10(6)/l and 0.16 x 10(6)/l were required if regular (10 1) and large-volume (media n 20 1) leukaphereses were performed, respectively. Conclusion: These results contribute to the further optimization of stem ce ll therapy since - depending on the tumor entity - they allow to estimate t he expected stem cell yield before the mobilization therapy is administered .