Similar breast cancer cell contamination of single-day peripheral-blood progenitor-cell collections obtained after priming with hematopoietic growth factor alone or after cyclophosphamide followed by growth factor

Purpose: To evaluate tumor-cell contamination of peripheral-blood progenitor-cell (PBPC) collections obtained after priming with granulocyte colony-stimulating factor (G-CSF). Patients and Methods: Immunocytochemical (ICC) and tumor clonogenic (TCA) assays were used to analyze tumor-cell contamination of pretreatment peripheral-blood (PB) and bone marrow (BM) samples, and of PBPC collection samples obtained after priming with G-CSF 5 μg/kg/d for 5 or 7 days in 38 women with advanced breast cancer undergoing high-dose chemotherapy (HDC). Results were compared with 37 historical control patients who underwent PBPC mobilization with cyclophosphamide (4 g/m²) followed by granulocyte-macrophage colony-stimulating factor (GM-CSF) 5 μg/kg/d for 14 days. Results: Before PBPC priming with G-CSF, only one of 37 (3%) PB and four of 36 (11%) BM samples had tumor cells detected by ICC. Tumor-cell contamination of PBPC collections obtained after 5 or 7 days of G- CSF priming was observed in only three of 38 patients (8%). All patients with tumor cells detected in the PBPC collection had stage IV disease. Cells with in vitro clonagenic potential were detected only in the pretreatment BM sample in one patient, and another two patients had ICC- and TCA-positive PBPC samples despite tumor-negative PB and BM before priming. These results are similar to those previously reported for PBPC primed with cyclophosphamide and GM-CSF. Conclusion: in patients with advanced breast cancer responsive to cytotoxic chemotherapy, tumor-cell contamination is not increased in PBPC collected after 5 or 7 days priming with G-CSF and appears similar to that seen when PBPC are primed with cyclophosphamide followed by GM-CSF.