BACKGROUND: Oral squamous cell carcinoma (OSCC) is a type of malignancy characterized by high relapse and recurrence rates in the late stage despite optimal surgical intervention and postoperative chemoradiotherapy. Because the management of relapse following definitive treatment is challenging, accurate risk stratification is of clinical significance to improve treatment outcomes. Circular RNAs (circRNAs) are noncoding RNAs featured with cell-type specificity and high stability, owing to their circular structure, making these molecules excellent biomarkers for a variety of diseases. METHODS: The levels of hsa_circ_0000190 and 0001649 in plasma samples from 30 healthy controls and 66 OSCC patients were determined by droplet digital polymerase chain reaction. The same primer sets were used with PCR to examine the expression of these two circRNAs in cancerous and adjacent normal tissues. A receiver operating characteristics curve was generated to evaluate the diagnostic value. The Kaplan-Meier method with a log-rank test was used for survival analysis. RESULTS: We identified two circRNAs as potential biomarkers for OSCC, showing that the plasma level of hsa_circ_0000190 was significantly decreased in the late stage and marginally correlated with the development of second primary OSCC. We also found that the decreased plasma hsa_circ_0001649 was correlated with the recurrence and poor prognosis of patients. Additionally, we found that high plasma hsa_circ_0000190, but not hsa_circ_0001649, possibly predicted a better response of patients to induction chemotherapy. CONCLUSION: Our study demonstrated the potential of biomarkers in plasma to inform not just the tumor but the entire oral cavity, thereby offering a prediction for early recurrence and second primary OSCC. The plasma circRNAs remain valuable for OSCC, albeit the easy accessibility to the oral cavity.
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