Circulating tumor cells and emerging blood biomarkers in breast cancer

Purpose of review To critically review the latest findings concerning the role of circulating tumor cells (CTCs) and other blood biomarkers in breast cancer. Recent findings CTCs are epithelial tumor cells detected in the peripheral blood of patients with solid tumors using mainly cytometric/antibody-based and molecular approaches. Most technologies for CTC detection, including the FDA-approved CellSearch, are only detecting epithelial cell adhesion molecule (EpCAM)-positive CTCs and may miss clinically relevant subpopulations of CTCs. The value of CTC detection by CellSearch in metastatic breast cancer (MBC) may depend on the clinical setting and regimen used. In a retrospective analysis of 516 patients with MBC, CTC detection did not predict clinical outcome in chemo-naïve women with HER2-positive MBC treated with anti-HER2 therapy, but had prognostic value in other breast cancer subtypes. Similarly, changes in CTCs during treatment did not predict outcome in 67 women treated with first-line bevacizumab/chemotherapy. CTC detection by CellSearch before or after adjuvant chemotherapy was associated with worse disease-free survival in 1489 patients with early breast cancer. Circulating nucleic acids, microRNAs and genomic rearrangements have been suggested as promising blood biomarkers. Summary Currently, there is no role for CTCs in clinical practice. The clinical utility of CTCs and other blood biomarkers should be prospectively tested.