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BACKGROUND: Oral cavity squamous cell carcinoma (OCSCC) is the most common head and neck malignancy. Although the survival rate of patients with advanced-stage disease remains approximately 20% to 60%, when detected at an early stage, the survival rate approaches 80%, posing a pressing need for a well validated profiling method to assess patients who have a high risk of developing OCSCC. Tumor DNA detection in saliva may provide a robust biomarker platform that overcomes the limitations of current diagnostic tests. However, there is no routine saliva-based screening method for patients with OCSCC. METHODS: The authors designed a custom nextgeneration sequencing panel with unique molecular identifiers that covers coding regions of 7 frequently mutated genes in OCSCC and applied it on DNA extracted from 121 treatment-naive OCSCC tumors and matched preoperative saliva specimens. RESULTS: By using stringent variant-calling criteria, mutations were detected in 106 tumors, consistent with a predicted detection rate ≥88%. Moreover, mutations identified in primary malignancies were also detected in 93% of saliva samples. To ensure that variants are not errors resulting in false-positive calls, a multistep analytical validation of this approach was performed: 1) re-sequencing of 46 saliva samples confirmed 88% of somatic variants; 2) no functionally relevant mutations were detected in saliva samples from 11 healthy individuals without a history of tobacco or alcohol; and 3) using a panel of 7 synthetic loci across 8 sequencing runs, it was confirmed that the platform developed is reproducible and provides sensitivity on par with droplet digital polymerase chain reaction. CONCLUSIONS: The current data highlight the feasibility of somatic mutation identification in driver genes in saliva collected at the time of OCSCC diagnosis.

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6562 Background: Oral cavity squamous cell carcinoma (OCSCC) frequently presents as clinically advanced disease with poor prognosis. When diagnosed at early stages, survival rates approach 80%, underscoring the need for validated, cost-effective detection methods. OCSCC is driven by the serial acquisition of genetic alterations. Tumor-defining somatic mutations are attractive biomarkers and hence their presence in saliva may be associated with malignancy as shown in a few proof-of-concept studies, including our previous work. Based on this premise, we present a low-cost, accurate, next generation sequencing (NGS) test with high clinical utility aimed at detecting mutations in the saliva for early diagnosis and potential screening of OCSCC. Methods: We have designed a custom NGS panel that covers exons of 7 most frequently mutated genes in OSCC. This minimal gene set derived from the analysis from 3 public datasets, predicted incidence of at least one somatic aberration in 89% of patients. We recruited 91 treatment-naïve OCSCC patients and profiled DNA from tissue and matched pre-operative saliva using this test. We also tested DNA from 12 subjects with premalignant lesions with high-grade oral dysplasia and matched saliva. Results: Using stringent variant calling criteria, at least one somatic variant was detected in 88 (96%) of the 91 primary tumors. 90.9% of the matched saliva were concordant, with only a minor decrease in early stage disease. Tumor-specific mutations (≥5% AF) in driver genes were detected in 10 (83.3%) dysplastic lesions, suggesting that driving clonal events may occur early in disease development. Interestingly, in 3 matched saliva of the dysplastic samples, the same mutations were detected. To ensure a variant is not a false positive call, we performed a vigorous multistep analytical validation of this saliva-based test: (i) independent re-sequencing of 24 saliva confirmed 94% reproducibility; (ii) no functionally relevant variants were detected in saliva from 12 of 13 healthy subjects without history of tobacco and alcohol usage; (iii) reproducibility, sensitivity, and specificity were confirmed using a positive control with 7 loci at 0.25% AF across 8 independent saliva sequencing runs and a certified negative control and was found to be on par with droplet digital PCR. Conclusions: These data highlight the feasibility of saliva-based testing for early diagnosis of OCSCC and premalignant lesions.

Tumour metastasis is one of the leading cause of cancer-related mortality. Circulating tumour cells (CTCs) have been implicated in loco-regional and distant metastasis and its role is being extensively studied in various malignancies, including those from the head and neck region. The main challenge in understanding their significance lies in the rarity of these cells in the blood. However, newer technologies have attempted to overcome these pitfalls. This review explores the evolution of CTC research and other related areas, including its biological significance, sustainability within the circulating vascular environment and possible clinical implications.