Circulating biomarkers in oral cancer: Unravelling the mystery

Oral squamous cell carcinoma (OSCC) is among the most common malignancies and a leading cause of death in developing countries. Late diagnosis and regional and/or distant metastasis worsen the prognosis of this condition. Despite the advances in diagnostic modalities and management strategies, there is little improvement in the 5-year survival rate. A deeper insight into the molecular events of various tumours has enabled the use of minimally invasive methods for monitoring disease progression, prognostication and treatment monitoring. Although studies in OSCC are preliminary, the use of liquid biopsies has opened new frontiers for the development of biomarkers that can serve as alternatives to conventional biopsies and imaging methods. Circulating biomarkers in blood allow for the real-time monitoring of tumour and therapeutic responses. This review aims to outline the promises and challenges of circulating biomarkers in OSCC with special emphasis on circulating tumour cells, circulating tumor DNA, and exosomes.