Immunohistochemical detection of breast cancer cells in paired peripheral blood progenitor cell specimens collected after cytokine or cytokine and myelosuppressive chemotherapy

Mobilized peripheral blood progenitor cells (PBPC) from 30 patients with advanced breast cancer were studied for the presence of tumor cell contamination using a highly sensitive immunohistochemical technique with the capacity to detect one tumor cell in one million mononuclear cells, Aliquots of PBPC were obtained after 4 days of G-CSF and/or GM-CSF and again during G-CSF-stimulated recovery from myelosuppressive doses of cyclophosphamide, The overall incidence of tumor cell contamination was 23%, occurring in PBPC specimens from seven of 30 patients. All four cases in which tumor cells were detected after mobilization with cytokine alone also had tumor cells detected in PBPCs collected following chemotherapy and G-CSF, There were three cases in which malignant contamination was detected only in the specimens collected after cyclophosphamide, There was a greater frequency of tumor cell contamination in aphereses performed during G-CSF-stimulated recovery from cyclophosphamide than in collections primed by cytokine alone (13% vs 23%; P = 0.08), although this did not reach statistical significance. This trend suggests that collection of PBPC during cytokine-stimulated recovery from myelosuppressive chemotherapy may be associated with a greater risk of contamination with malignant cells than apheresis during mobilization with cytokines in the steady state.