Longitudinal monitoring of circulating tumor cell phenotypic conversion as a predictor of late recurrence in breast cancer: a prospective feasibility study using the GenoCTC platform.

PURPOSE: Patients with hormone receptor-positive (HR+) breast cancer faces a persistent, constant risk of distant recurrence for over 20 years. This proof-of-concept study evaluated the clinical utility of circulating tumor cell (CTCs) monitoring using the GenoCTC® platform to detect molecular precursors of late recurrence in long-term breast cancer survivors. METHODS: Blood samples from 25 breast cancer patients in recurrence-free survival (RFS), 4-13 years post-surgery, were analyzed using the GenoCTC® platform with EpCAM and Vimentin as markers. Baseline CTCs were characterized by immunofluorescence staining (DAPI+/Cytokeratin (CK)+/CD45-). A subset of eight initially CTC-negative patients underwent longitudinal follow-up assay at a 5-year interval, with expanded profiling including c-MET enrichment. CTCs counts were correlated with clinicopathological variables, receptor status and clinical outcomes. RESULTS: At baseline, CTCs were detected in 24% of patients. CTC burden was significantly associated with recurrence (P <.0001) and mortality (P = .0016). A high CTC count was identified in all recurrence events (P = .003). In longitudinal follow-up, 6 of 8 (75%) initially CTC-negative patients demonstrated "molecular conversion" characterized by a "burst" of epithelial-mesenchymal hybrid CTCs, including CK+/Vimentin+ and cMET+ populations. CONCLUSION: Longitudinal phenotypic CTC profiling could identify a pre-clinical "molecular conversion" in breast cancer survivors, which has the potential to provide a time lead over radiographic appearance of recurrence. Integration of EpCAM, Vimentin and cMET multi-marker CTC monitoring into standard long-term follow-up may enable early interception of dormancy escape and late relapse.