Background & objective: Recently, immunocytochemistry and immunomagnetic enrichment have been used in detecting circulating tumor cells (CTCs). This study was designed to investigate the sensitivity and specificity of modified immunomagnetic enrichment of tumor cells in combination with fluorescent immunocytochemistry in detecting CTCs in peripheral blood of patients with breast cancer.
Methods: The sensitivity of this detection method was evaluated by sparking breast carcinoma cell line MCF-7 into normal peripheral blood. Mononuclear cells were isolated from peripheral blood of 52 naive breast cancer patients and 20 healthy female volunteers. Epithelial cell adhesion molecule (EpiCAM) antibody (Ab), covalently bound to magnetic beads, was used to enrich CTCs expressing EpiCAM antigen. CTCs, indicated by positive staining of cytokeratin (CK) 8/18 (green fluorescence), was detected by modified fluorescent immunocytochemistry, and confirmed by DAPI nuclear staining (deep blue).
Results: The sensitivity of immunomagnetic enrichment with fluorescent immunocytochemistry was so high that 1 tumor cell in 1x10(7) peripheral blood mononuclear cells could be detected. The specificity of this method was 100%. Positive rate of CTCs was significantly higher in peripheral blood of the patients than in peripheral blood of the healthy volunteers (53.8% vs. 0, P<0.001). The presence of CTCs was correlated positively with clinical stage (P<0.001) and axillary lymph node status (P<0.005), and irrelevant with other prognostic factors (P>0.05).
Conclusions: Modified immunomagnetic enrichment of tumor cells in combination with fluorescent immunocytochemistry is a time-saving, easily-performed, sensitive and specific method for detecting CTCs in peripheral blood of breast cancer patients. The presence of CTCs in peripheral blood correlates positively with clinical stage and axillary lymph node status of breast cancer patients.