There were no significant associations with tumor recurrence and TNM stage in the detection of ctDNA at the time of initial diagnosis (Stage I–II vs. III–IV; 3/9 vs. 7/11, p = 0.36, T1–2 vs. T3–4; 5/11 vs. 5/9, p = 1.0, N0 vs. N1; 8/15 vs. 2/5, p = 1.0) Because of the different N staging between p16-positive and -negative cases, the actual number of metastatic lymph nodes before treatment was assessed using CT imaging and was not related to the detection of ctDNA. This evidence concerns the gene CDKN2A and neoplasm.