Increase of monocytes predicts mobilization of peripheral stem and progenitor cells after chemotherapy followed by G‐CSF administration

Mobilization of primitive haematopoietic cells to the peripheral blood was studied in 25 patients with haematological malignancies. The optimal level of peripheral stem cells (PSC), defined by their surface expression of CD34, was significantly higher after mobilization with G-CSF, either following chemotherapy or alone (median: 123×10 6 /l and 143×10 6 /l of CD34 + cells respectively) than without administration of G-CSF subsequent to chemotherapy (median: 27×10 6 /l of CD34 + cells). An individual variation in when optimal mobilization of CD34 + cells and myeloid progenitors occurs after chemotherapy and G-CSF administration was noted (median: day 12, range 7-24 days), which makes it difficult to predict when PSC collections in a given patient should be performed. In this study, chemotherapy followed by G-CSF administration resulted in a short lasting (2-3 days) peak appearance of CD34 + cells that could predicted by a 2-fold increase in absolute numbers of monocytes, as compared to the previous day. After the peak level of CD34 + cells in the blood was reached, no further increase in monocytes was seen. The identification of an increase in monocytes, to be used as a predictive variable for when optimal mobilization of PSC will occur in a given patient, may be particularly useful in the individual timing of PSC collections from non-hospitalized patients