title: Can biomarker assessment on circulating tumor cells help direct therapy in metastatic breast cancer?
abstract: Circulating tumor cell (CTC) count has prognostic significance in metastatic breast cancer, but the predictive utility of CTCs is uncertain. Molecular studies on CTCs have often been limited by a low number of CTCs isolated from a high background of leukocytes. Improved enrichment techniques are now allowing molecular characterisation of single CTCs, whereby molecular markers on single CTCs may provide a real-time assessment of tumor biomarker status from a blood test or "liquid biopsy", potentially negating the need for a more invasive tissue biopsy. The predictive ability of CTC biomarker analysis has predominantly been assessed in relation to HER2, with variable and inconclusive results. Limited data exist for other biomarkers, such as the estrogen receptor. In addition to the need to define and validate the most accurate and reproducible method for CTC molecular analysis, the clinical relevance of biomarkers, including gain of HER2 on CTC after HER2 negative primary breast cancer, remains uncertain. This review summarises the currently available data relating to biomarker evaluation on CTCs and its role in directing management in metastatic breast cancer, discusses limitations, and outlines measures that may enable future development of this approach.
authors.affiliation: Sandro Pitigliani Medical Oncology Department, Prato Hospital, Istituto Toscano Tumori, Via Ugo Foscolo, Prato, PO 59100, Italy. nhturner@usl4.toscana.it.
authors.forename: Natalie
authors.initials: N
authors.lastname: Turner
authors.affiliation: Sandro Pitigliani Medical Oncology Department, Prato Hospital, Istituto Toscano Tumori, Via Ugo Foscolo, Prato, PO 59100, Italy. mpestrin@usl4.toscana.it.
authors.forename: Marta
authors.initials: M
authors.lastname: Pestrin
authors.affiliation: Translational Research Laboratory, Prato Hospital, Via Ugo Foscolo, Prato, PO 59100, Italy. fgalardi@usl4.toscana.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Galardi
authors.affiliation: Translational Research Laboratory, Prato Hospital, Via Ugo Foscolo, Prato, PO 59100, Italy. frdeluca@usl4.toscana.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: De Luca
authors.affiliation: Sandro Pitigliani Medical Oncology Department, Prato Hospital, Istituto Toscano Tumori, Via Ugo Foscolo, Prato, PO 59100, Italy. lmalorni@usl4.toscana.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Malorni
authors.affiliation: Sandro Pitigliani Medical Oncology Department, Prato Hospital, Istituto Toscano Tumori, Via Ugo Foscolo, Prato, PO 59100, Italy. adileo@usl4.toscana.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Di Leo