Saliva-based cell-free DNA and cell-free mitochondrial DNA in head and neck cancers have promising screening and early detection role

Background: Cell-free DNA (cfDNA) and cell-free mitochondrial DNA (cf-mtDNA) have been postulated as potential diagnostic and prognostic biomarkers for different human malignancies. Early detection of head and neck malignancies is fundamental for optimal patient management. This study, therefore, aimed to assess the utility of saliva-based liquid biopsy as a noninvasive source of cfDNA and cf-mtDNA for detecting head and neck cancer (HNSCC). Methods: One hundred thirty-three patients diagnosed with either oral leukoplakia (OLK) or HNSCC were compared with 137 healthy volunteers. An unstimulated whole saliva sample was collected from each participant. The absolute copy numbers of salivary cf-mtDNA and cfDNA were quantified using Multiplex Quantitative PCR. Two diagnostic indices based on the investigated molecules were assessed for their ability to differentiate between different diagnostic categories. Results: The median scores of cfDNA and cf-mtDNA were statistically significantly higher among HNSCC patients (p < 0.05), revealing area under the curve values of 0.758 and 0.826, respectively. The associated accuracy for this test in discriminating HNSCC from other diagnostic categories was 77.37% for the cfDNA-based index and 80.5% for the cf-mtDNA-based index. The median score of cfDNA was statistically significantly higher for patients with severe epithelial dysplasia (OED) compared to those with epithelial keratosis with no OED and mild OED. However, there was no significant difference between controls and OLK individuals. Conclusion: cfDNA and cf-mtDNA showed potential for use as precision medicine tools to detect HNSCC. Further multi-centre prospective studies are warranted to assess the prognostic utility of these molecules.