Biological effects of pegfilgrastim after myelosuppressive chemotherapy in breast cancer

10521 Background: The dose and schedule of chemotherapy (CT), that play a crucial role in the outcome of pts with chemosensitive tumors, were made feasible with the primary use of colony stimulating factors. Few data are available on the in vivo biological effects of the “long-lasting” cytokine pegfilgrastim. We have focused on the cytokinetic effects on the CD34+/38+ peripheral blood (PB) progenitor cell subset and on its influence on neutrophils functional parameters. Methods: We studied PB samples from 14 breast cancer pts (median age 47 yrs; 35–61 yrs), treated with Docetaxel (80 mg/sqm, d 1) + Epirubicin (75 mg/sqm, d 1) + pegfilgrastim (6 mg s.c. on d +1). The % of CD34+/38+ circulating progenitor cells (CPCs) (sorted with immunomagnetic procedure) undergoing G0/G1, S and G2/M phases of the cell cycle or showing apoptotic features were evaluated using flow cytometry. Annexin V was quantitated at a single cell level and correlated with cell cycle phases. On PB buffy coat smears, alkaline phosphatase ...