Comparison of RNA Marker Panels for Circulating Tumor Cells and Evaluation of Their Prognostic Relevance in Breast Cancer.

Liquid biopsy is a promising tool for therapy monitoring of cancer patients, but a need for further research in this field exists in order to improve sensitivity, specificity, standardization and minimize costs. In our present study, we evaluated two panels of transcripts related with the presence of circulating tumor cells (CTCs) (Panel 1: , , and Panel 2: , , , , and ) in two cohorts of breast cancer patients (metastatic and early). A blood cell fraction possibly containing CTCs was isolated with density gradient centrifugation, followed by RNA isolation and qPCR using TaqMan or RT-qPCR using hybridization probes. The positivity rates of the investigated panels were similar, albeit higher in metastatic (69.4% Panel 1, 75.0% Panel 2; total 86.1%) compared to early (18.9% Panel 1, 23.3% Panel 2; total 31.1%) breast cancer patients. , , , , , and individually correlated with shorter overall survival in the metastatic patient cohort. The findings highlight the additional value of Panel 2 markers, which are in contrast to and not solely linked to an epithelial phenotype.