Circulating Tumor Cells (CTCs): From Detection to Dissection

Summary �䀆e breast cancer represents one of the most prevalent cancers in the world. �䀆e outlook for patients diagnosed with breast cancer has been changing for the better over time, with several sgnficant advances coming through in the past 10 years; among them, and a�怇er highlighting the importance of prevention and early diagnosis, relevant advances as a better understanding of the process through gene expression analysis, at the ability to use specfic therapeutic targets, and a more advanced hormonal therapy played a more than sgnficant positive role. Nevertheless, and despite the above mentioned improvements in treatment and prevention, breast cancer remains one of the leading causes of cancer mortality in women. Approximately 90% of cancer mortality is due to the development of metastatic disease. �䀆e metastatic process involves the discharge of tumor cells from the primary tumor into peripheral blood (circulating tumor cells, CTCs) to a target organ (1). Recently, the clinical implication of detection of CTCs in breast cancer has been recognized and accepted (2). In fact, the presence of CTCs has been correlated with a worse prognosis in early and metastatic breast cancer. As a result of these investigations, it has been reported that the amount of CTCs in the blood of these patients is an independent prognostic marker for overall survival and progression-free survival (OS and PFS) (3). However, despite the accepted role of CTCs in the prognosis of breast cancer, the detection of CTCs alone does not provide enough information. Although the changes in CTC's amount per blood unit might indicate sensitivity or resistance to an anticancer therapy and provides information about the prognosis of the disease, this information is in many cases not enough (4). �䀆e question we need to ask is, "how can we eliminate these CTCs in order to combat the disease" �䀆e "annihilation of CTCs", involves the knowledge of their biology. �䀆e molecular and phenotypic characterization of these CTCs could be the key to understanding the mechanism of resistance to administered therapies and the door to the development of novel cancer treatments that specficalltarget circulating tumor cells. In this short communication, we would like to brefldiscuss the relevance of the molecular characterization of CTCs. Firstly, as new tools to potential clinical use in the monitoring of breast cancer, and secondly as potential biomarkers to development of new therapeutic targets. Similar but not identical