Circulating Tumor Cells Detected Using EpAb3-5 as Prognostic Indicators in Head and Neck Squamous Cell Carcinoma.

Background: EpAb3-5, an anti-EpCAM (epithelial cell adhesion molecule) neutralizing antibody, enhances circulating tumor cell (CTC) detection, but its clinical and prognostic relevance in head and neck squamous cell carcinoma (HNSCC) remains unclear. Methods: We retrospectively analyzed 66 HNSCC patients. CTCs were enumerated using EpAb3-5 and a commercial EpCAM-based platform (MACS), and tumor EpCAM expression detected using EpAb3-5 was assessed by immunohistochemistry. Associations with clinicopathologic features were evaluated, and survival outcomes were analyzed using Kaplan-Meier and Cox regression models, truncated at five years. Results: EpAb3-5 detected significantly more CTCs than MACS (p < 0.001), indicating greater detection sensitivity. Tumor EpCAM expression detected by EpAb3-5 correlated with nodal status (p < 0.01) but not T classification or overall stage. Although EpAb3-5-detected EpCAM expression alone was not an independent predictor of overall survival (OS) or disease-free survival (DFS), its integration with tumor staging revealed a context-dependent prognostic association. Specifically, low EpCAM expression assessed using EpAb3-5 identified early-stage patients with better OS (p < 0.05), whereas no significant survival differences were observed in advanced-stage disease. Conclusions: EpAb3-5 enhances CTC detection compared with a conventional EpCAM-based method and provides complementary prognostic information when interpreted alongside tumor staging. These findings indicate that EpCAM immunoreactivity assessed using EpAb3-5 may assist in refining risk stratification in early-stage HNSCC; however, these observations should be considered exploratory and warrant further validation in larger prospective cohorts.