Circulating tumor cell analysis for early detection of minimal residual disease in oral cancer

Background: The key clinical problem in detecting minimal residual disease (MRD) in oral cancer (OC) patients is the lack of sensitive, standardized tools to identify residual cancer cells that remain after treatment but are undetectable by conventional imaging or pathology. We aim to assess whether circulating tumor cells (CTCs) can serve as a biomarker for early detection of MRD. Methods: This longitudinal observational study collected blood samples from 50 OC patients at baseline, and at one, three, and twelve months following surgery. CTCs were isolated using a spiral microfluidic device that leverages inertial microfluidic principles for separation. CTC was defined as either pan-cytokeratin (CK+) or cell-surface vimentin (CSV+), DAPI positive and CD45 negative. The presence of CTCs was compared between patients who experienced recurrence and those who remained disease-free. Results: At one month, patients with recurrence showed significantly higher total CTC counts (mean 2.75 vs 0.61; p = 0.0021) and significantly elevated CTC phenotype positivity (cytokeratin positive (CK+) cell surface vimentin positive (CSV+): p = 0.0001). At three months, CTC differences further widened (mean 8.0 vs 0.91; p = 0.0042), with strong separation across multiple CTC cluster phenotypes, including CK-CSV+ (p = 0.0001) and CK+CSV+ (p = 0.0003). Significant CTC-based differences persisted at one year (p = 0.0241). Conclusions: CTCs demonstrate strong promise as early biomarkers for MRD and impending recurrence in OC. Multiple markers exhibit statistically significant separation well in advance of conventional clinical detection, highlighting their potential for early intervention, supporting its integration into routine clinical practice for improved patient outcomes.