Hematopoietic progenitor cell collection and neoplastic cell contamination in breast cancer patients receiving chemotherapy plus granulocyte-colony stimulating factor (G-CSF) or G-CSF alone for mobilization

Background: We compared hematopoietic progenitor cell (HPC) collection and neoplastic cell contamination in breast cancer patients given cyclophosphamide (CTX) plus granulocytecolony stimulating factor (G-CSF) or G-CSF alone for mobilization. Patients and methods: In 57 stage II-III breast cancer patients, CD34+ cells, colony-forming units-granulocyte macrophage (CFU-GM), early HPC and breast cancer cells were counted in HPC collections obtained after CTX plus G-CSF (n = 27) or G-CSF-alone mobilization (n = 30). Results: The CD34+ cell collection was about two-fold greater after CTX plus G-CSF mobilization (11.0 ± 7.9 vs. 5.8 ± 3.5 x 10⁶/kg, P <0.001). Similarly, the total number of CFUGM, CD34+CD38- cells and of week-5 cobblestone area forming cells (CAFC) collected was significantly higher in patients mobilized with CTX plus G-CSF. Breast cancer cells were found in the apheresis products of 22% of patients mobilized with CTX plus G-CSF and in 10% of patients mobilized with G-CSF alone (P = 0.36). Of seven patients who failed G-CSF-alone mobilization and eventually underwent chemotherapy plus G- CSF mobilization, none had cytokeratin-positive cells after G-CSF mobilization, whereas four out of seven had cytokeratin-positive cells after chemotherapy plus G-CSF (P = 0.07 by χ² test). Conclusion. The CTX plus G- CSF mobilization protocol was associated with a significantly higher HPC collection. However, this benefit was not accompanied by a reduction in the incidence of tumor-contaminated HPC graft.