title: Clinical implications of circulating tumor cells of breast cancer patients: role of epithelial-mesenchymal plasticity.
abstract: There is increasing interest in circulating tumor cells (CTCs) due to their purported role in breast cancer metastasis, and their potential as a "liquid biopsy" tool in breast cancer diagnosis and management. There are, however, questions with regards to the reliability and consistency of CTC detection and to the relationship between CTCs and prognosis, which is limiting their clinical utility. There is increasing acceptance that the ability of CTCs to alter from an epithelial to mesenchymal phenotype plays an important role in determining the metastatic potential of these cells. This review examines the phenotypic and genetic variation, which has been reported within CTC populations. Importantly, we discuss how the detection and characterization of CTCs provides additional and often differing information from that obtained from the primary tumor, and how this may be utilized in determining prognosis and treatment options. It has been shown for example that hormone receptor status often differs between the primary tumor and CTCs, which may help to explain failure of endocrine treatment. We examine how CTC status may introduce alternative treatment options and also how they may be used to monitor treatment. Finally, we discuss the most interesting current clinical trials involving CTC analysis and note further research that is required before the breast cancer "liquid biopsy" can be realized.
authors.affiliation: School of Surgery, The University of Western Australia , Perth, WA , Australia.
authors.forename: Linda M
authors.initials: LM
authors.lastname: McInnes
authors.affiliation: School of Surgery, The University of Western Australia , Perth, WA , Australia.
authors.forename: Natalie
authors.initials: N
authors.lastname: Jacobson
authors.affiliation: Medical Oncology, Royal Perth Hospital , Perth, WA , Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Redfern
authors.affiliation: Department of Medical Oncology, St Vincent's Hospital Melbourne , Melbourne, VIC , Australia.
authors.forename: Anthony
authors.initials: A
authors.lastname: Dowling
authors.affiliation: Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology , Brisbane, QLD , Australia ; St. Vincent's Institute , Melbourne, VIC , Australia ; Department of Surgery, St Vincent's Hospital, University of Melbourne , Melbourne, VIC , Australia.
authors.forename: Erik W
authors.initials: EW
authors.lastname: Thompson
authors.affiliation: School of Surgery, The University of Western Australia , Perth, WA , Australia.
authors.forename: Christobel M
authors.initials: CM
authors.lastname: Saunders
keywords: breast cancer; circulating tumor cells; clinical application; epithelial–mesenchymal transition; metastasis