Abstract
Oral cancer is one of the most prevalent forms of cancer worldwide. Carcinogenesis is a complex process, in which heterogeneity plays an important role in the development and progression of the disease. This review provides an overview of the current biological and clinical significance of circulating tumour cells (CTCs), circulating tumour DNA (ctDNA), and exosomes for diagnosis and prognosis of oral cancer. We highlight the importance of liquid biopsy—using blood and saliva—which represents a potential alternative to solid biopsy for diagnosis and prognosis. Moreover, liquid biomarkers allow for the real-time monitoring of tumour evolution and therapeutic responses, initiating the era of personalized medicine. However, in oral cancer, the impact of liquid biopsies in clinical settings is still limited, requiring further studies to discover the best scenario for its clinical use.
Highlights
Oral cancer is one of the most prevalent forms of cancers worldwide, showing an incidence and mortality twice as high in men (2.3% and 1.7%, respectively) compared to women (1.2% and 0.8%, respectively) [1]
circulating tumour cells (CTCs) detection was significantly correlated with tumour size, whereas disseminated disseminated tumour cells (DTCs) were significantly correlated with the nodal status
CTCs and DTCs were significantly associated with the presence of distant metastasis, no statistically significant association was found with the overall survival and the time of relapse or death, probably due to the small sample size
Summary
Oral cancer is one of the most prevalent forms of cancers worldwide, showing an incidence and mortality twice as high in men (2.3% and 1.7%, respectively) compared to women (1.2% and 0.8%, respectively) [1]. Kulasinghe et al [51] evaluated by spiral microfluidic technology the CTC levels in 60 treatment-naive head and neck cancer patients (40% in the oral cavity), including early and late tumour stages. Grisanti et al [35] observed in patients with locally advanced and recurrent metastatic head and neck cancer (32% of the oral cavity) that EGFR expression could be modulated over time, with the presence of EGFR at any time point being low (45%) when compared with the primary tumour, which could identify cancer cells that were more likely to metastasize. SHOX2 and SPEPT9 are the methylation markers with the highest level of validation in biofluids of different cancers remote from the oral cavity [70,71] Both biomarkers have been validated in a large prospective cohort of 649 head and neck cancer patients as valuable biomarkers for tumour diagnosis, showing 59% of patients as methylation-positive at 96% specificity. Several methods have been developed to detect ctDNA, but there is still a lack of a standardized method, which is essential for its clinical application together with the need of reducing the analysis cost
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