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Circulating Tumor DNA in Saliva in an Orthotopic Head and Neck Cancer Mouse Model

Aim: To evaluate the feasibility of conducting studies of saliva circulating tumor DNA (ctDNA) as a biomarker of metastasis or recurrence in our orthotopic head and neck cancer (HNC) mouse model. Materials and Methods: A mouse model of recurrence or metastasis after tongue cancer resection was developed. Blood and saliva were collected at baseline and at the establishment of recurrence or metastasis. Real-time polymerase chain reaction was performed to quantify human long interspersed element (hLINE) in samples to assess the amount of ctDNA. Results: In our model, salivary hLINE increased as the cancer developed and decreased after surgery. Plasma hLINE was significantly elevated in mice with metastasis. The presence of tongue cancer recurrence in mice was more correlated with hLINE concentration in saliva than in plasma. Conclusion: In our orthotopic model, salivary ctDNA better reflected tumor development and recurrence than did plasma ctDNA.