Updates of liquid biopsy in oral cancer and multiomics analysis

Liquid biopsy is a method sampled from body fluids, such as blood, saliva, urine, pleural effusion, cerebrospinal fluid, and so on. It is minimally invasive and reproducible and therefore can build a dynamic, real-time monitoring of oral squamous cell carcinoma patient's conditions and treatment responses. Circulating tumor cells, circulating tumor DNA and exosomes are three main detection objects of liquid biopsy, having different detection methods and features involving cost, sensitivity, specificity and output. Blood and saliva are the options of liquid biopsy in oral cancer. Then we reviewed the studies of liquid biopsy in oral cancer, integrating multiomics analysis of these results. The multiomics analysis of genomics, transcriptomics, proteomics, metabolomics, and DNA methylation have shown potential for the early screening, diagnosis, staging, prognosis, personalized medicine therapy, and monitoring of recurrence (minimal residual disease). Besides, we concluded some problems to be solved, such as the lack of the standard of the measurement methods and procedures of samples, the insufficient connection among different omics, and how to improve the sensitivity and specificity. And we also put up rough assumptions to these problems. However, the analysis of multiomics of liquid biopsy in oral cancer still shows great clinical value in the diagnosis and treatment of oral squamous cell carcinoma.