Circulating Tumor Cells in Head and Neck Cancer

Circulating tumor cells (CTCs) are a rare subpopulation of cells with potential use in a range of clinical applications for better management of patients with cancers. For example, they have been recognized as a clinical biomarker, preclinical model, and therapeutic target as they maintain underlying tumor heterogeneity and mimic malignant characteristics. Though CTCs have been well studied in metastatic breast, prostate, and colorectal cancer patients, a lack of research and information remains in head and neck cancer (HNC). Limited evidence suggests that CTCs have been identified as a potential marker for early metastatic disease, response to treatment, and patient survival. In addition, CTCs can be act as a good candidate leading to treatment failure and cancer regression in HNC. Detection of CTCs as liquid biopsies has significant clinical implication followed by analysis of expression pattern of epithelial markers and molecular characterization of CTCs. Also, a number of important aspects of cancer-specific treatment may be facilitated by the identification and characterization of CTCs, especially for patients with HNC. Thus, this chapter summarizes the current knowledge targeting the value and promise of evolving CTCs in clinical significance as a diagnostic and prognostic biomarker, therapeutic target, and also predictive biomarker in cancer relapse and treatment response focusing on HNC.