Administration of gm-csf to breast cancer patients mobilizes low numbers of tumor cells into leukapheresis harvests

Brugger et al (1994) reported that the administration of chemotherapy followed by G-CSF to patients (pts) with breast and lung cancer caused epithelial cells to appear in the circulation at a time dependent on whether bone marrow was involved with tumor. In this circumstance, it is, unclear if vascular damage caused by the chemotherapy contributes to the release of tumor cells. Consequently, we have evaluated mobilization of breast cancer cells into apheresis harvests in 15 pts with metastatic breast cancer following administration of GM-CSF alone. The tumor cells were detected by both immunocytochemistry(ICC) and RT-PCR to cytokeratins 8, 18 and 19. Blood and bone marrow were sampled prior to apheresis harvests and during cytokine administration, as well as, the pooled frozen sample administered to the patient and a blood sample immediately post-transplant. We observed positive apheresis harvests in pts with negative blood and marrow prior to mobilization. These results demonstrate that breast cancer cells are mobilized in low numbers, into leukapheresis harvests following the administration of cytokine alone and some tumor cells are likely to be re-infused with the harvest. However, the clinical significance of reinfusion of small numbers of mobilized tumor cells remains to be determined.