The Role of Liquid Biopsies for Monitoring Disease Evolution

Abstract

Body fluids of cancer patients have attracted increasing attention in biomedical research within the last 15 years since—as so-called liquid biopsies—they represent a non-invasive source of clinically exploitable biomarkers, including circulating tumor cells (CTCs) and cell-free tumor DNA (ctDNA). Assessment of CTCs in peripheral blood from solid cancer patients has proven useful for detection of subclinical disease which otherwise remains invisible for current staging techniques. Based on results from large cohort studies in breast and colon cancer, diagnostic tests for enumeration of CTCs have been developed which can be used for tumor staging, prognosis, and post-treatment surveillance. Circulating plasma DNA derived from Epstein–Barr or human papilloma viruses has been established as a sensitive and highly specific biomarker for early cancer detection and disease monitoring. More recently, first studies have been initiated for studying the diagnostic value of mutant variants in plasma-derived ctDNA for treatment selection, response assessment and early detection of treatment failure.Advanced Head and Neck Squamous Cell Carcinoma (HNSCC) represents a malignancy associated with locoregionally advanced stage at presentation, dismal prognosis and little improvement in treatment outcome over the past decade, especially for patients with metastatic disease. HNSCC patients might therefore benefit from incorporation of liquid biopsy-based assays in clinical management. In the following chapters, I will summarize current evidence of the diagnostic value of liquid biopsies in HNSCC and give examples of potential clinical applications.