Retracing Circulating Tumour Cells for Biomarker Characterization after Enumeration

Background Retracing and biomarker characterization of individual circulating tumour cells (CTCs) may potentially contribute to personalized metastatic cancer therapy. This is relevant when a biopsy of the metastasis is complicated or impos‐ sible to acquire. Methods A novel disc format was used to map and retrace individual CTCs from breast-cancer patients and nucleated cells from healthy blood donors using the CytoTrack platform. For proof of the retracing concept, CTC HER2 characterization by immunofluorescence was tested. Results CTCs were detected and enumerated in three of four blood samples from breast-cancer patients and the locations of each individual CTCs were mapped on the discs. Nucleat‐ ed cells were retraced on seven discs with 96.6%±8.5% recovery on five fields of view on each disc. Shifting of field of view for retracing was measured to 4-29 μm. In a blood sample from a HER2-positive breast-cancer patient, CTC enumeration and mapping was followed by HER2 charac‐ terization and retracing to demonstrate downstream immunofluorescence analysis of the CTC. Conclusion Mapping and retracing of CTCs enables downstream analysis of individual CTCs for existing and future cancer genotypic and phenotypic biomarkers. Future studies will uncover this potential of the novel retracing technology