Impact of circulating tumour cells on survival of eribulin-treated patients with metastatic breast cancer

Several clinical studies have examined circulating tumour cells (CTCs). However, the application of CTCs as a predictive/prognostic marker for breast cancer patients has yet to be established, particularly the selection of suitable markers for detecting CTCs. We recently investigated CTCs, including mesenchymal status, from metastatic breast cancer patients who had received eribulin-based treatment. We found that assessment of both mesenchymal and epithelial CTCs might be important for predicting eribulin responsiveness. In the current study, we followed up the outcomes of these patients after eribulin treatment and investigated the possibility of CTC analysis results serving as prognostic markers for this patient population. Twenty-one patients were enrolled and peripheral blood samples were collected before eribulin-based treatments. CTCs were then examined using a Microfluidic Chip device. CTCs positive for vimentin and pan-cytokeratin were defined as mesenchymal and epithelial CTCs, respectively. Overall survival (OS) was assessed in relation to the number of CTCs and clinicopathological factors. During the observation period, 13 patients (62%) died due to breast cancer and the median OS was 18 months. Patients with high-grade tumours and a high total number of CTCs showed significantly shorter OS than those with low-grade tumours and smaller CTC burdens (p = 0.026 and 0.037, respectively). Patients who received eribulin as the first chemotherapy for metastatic disease showed longer OS (p = 0.006). Our data suggest that determining numbers of both mesenchymal and epithelial CTCs might predict survival for patients receiving eribulin.