Studies on ctDNA found that increased ctDNA levels in samples also correlated with advanced stage and post-treatment recurrence rates; TP53 was the most commonly identified mutated gene in HPV-negative HNSCC; ctDNA was detected in saliva samples of all patients with oral HNSCC; and combined plasma and saliva liquid biopsy was the most sensitive method for detecting ctDNA [74,75]. The gene discussed is TP53; the disease is head and neck squamous cell carcinoma.