Circulating tumour cells as liquid biopsy in breast cancer—advancing from prognostic to predictive potential

Circulating tumour cells (CTCs) in breast cancer offer a unique opportunity to sample tissue that can derive from multiple sites in the body and may be more representative of the whole disease than a single standard biopsy. Their presence is now clearly associated with worse prognosis and can indicate treatment failure. Improved techniques to isolate single CTCs have also permitted in-depth molecular studies, revealing marked heterogeneity. Whilst giving a novel window into tumour evolution and resistance, it also raises new questions regarding treatment approaches. The ongoing challenge remains the translation of new information gleaned from CTCs into clinical benefit. © Springer Science+Business Media New York 2015.