ABSTRACT
BACKGROUND: Many patients with locoregionally advanced HPV-negative head and neck squamous cell carcinoma (HNSCC) relapse. Circulating tumor (ct)DNA has the potential to identify minimal residual disease, but its clinical utility for virus-negative HNSCC is not well understood. METHODS: We retrospectively evaluated a personalized, commercial ctDNA assay (Signatera™, Natera) during clinical care of patients treated for predominantly newly diagnosed HPV-negative HNSCC. Signatera™ utilizes 16-plex PCR from matched tumor and blood. Objectives were to understand ctDNA detectability and correlate changes post-treatment with disease outcomes. RESULTS: Testing was successful in 100/116 (86%) patients (median age: 65, 68% male, 65% smokers); testing failed in 16 (14%) due to insufficient tissue. Oral cavity (55, 47%) tumors were most common; most had stage III-IV disease (82, 71%) while 17 (15%) had distant metastases. Pre-treatment, 75/100 patients with successful testing (75%) had detectable ctDNA (range: 0.03-4049.69 MTM/mL). No clinical features predicted ctDNA detectability or levels (multivariate analysis). At median follow-up of 5.1 months (range: 0.2-15.1), 55 (55%) had >1 test result (range: 1-7; 194 samples). Of 55, 17 (31%) remained ctDNA positive after starting treatment. Progression-free survival was significantly worse for patients who were ctDNA positive vs. negative post-treatment (HR 7.33, 95%CI 3.12-17.2, p<0.001); 1-year overall survival was 89.1% vs. 100%, respectively (HR 7.46, 95%CI 0.46-119.5; p=0.155). CONCLUSIONS: Tumor-informed ctDNA testing is feasible in non-viral HNSCC. ctDNA positivity is an indicator of disease progression and associated with inferior survival. Further research is warranted to understand whether ctDNA may be leveraged to guide therapy in HNSCC.
