Cell line dependent expression of EpCAM influences the detection of circulating tumor cells with CellSearch

OBJECTIVES The existence of circulating tumor cells has emerged as an important factor for prognosis and survival. The CellSearch method is the only circulating tumor cell detection method approved by the US Food and Drug Administration for clinical use. It relies on the detection of EpCAM (epithelial cell adhesion molecule) and is approved for colon cancer, breast cancer and prostate cancer. We now investigated whether CellSearch can be used to quantify circulating tumor cells in head and neck squamous cell cancer. STUDY DESIGN AND METHODS In this study, we investigated the expression of EpCAM in 12 head and neck squamous cell cancer cell lines using Western blot and how this affected their detectability with CellSearch in peripheral blood. RESULTS We found a great variation in the expression of EpCAM between our head and neck squamous cell cancer cell lines. This was accompanied by variations in counting efficiency. CONCLUSION We suggest that for reliable quantification of circulating tumor cells in blood from patients with head and neck squamous cell cancer cell, an epitope independent method is preferable. LEVEL OF EVIDENCE NA.