Circulating tumor cells in breast cancer patients

Circulating tumor cells (CTCs) represent a potential non-invasive substitute for real-time tissue biopsy. Moreover, detection of CTCs in breast cancer patients has been reported as a strong prognostic factor. Biomarkers on CTCs have been analysed and correlated to tissue biopsies from breast cancer patients. Discordance in expression of potential biomarkers between primary tumor, metastatic sites and CTCs has been observed. Potential analytical confounding factors include lack of analytical consistency, varying sensitivities and specificities of used assays and differences in analytical ranges among various reported studies. Besides, clonal evolution within primary tumor (and metastatic sites) that leads to intratumor heterogeneity must be accounted for. Nevertheless, several on-going trials are exploring CTCs detection and biomarker profiling in view of personalising cancer treatment based on these real-time results. In this work, we will review CTCs in breast cancer patients and focus on identification of novel prognostic biomarkers.