e18035 Background: Head and neck squamous cell carcinoma (HNSCC) is clinically heterogeneous with significant morbidity and mortality, particularly in medically underserved populations. Circulating tumor DNA (ctDNA) is a non-invasive biomarker for disease monitoring and minimal residual disease detection. We evaluated a personalized, tumor-informed ctDNA assay in HNSCC patients at an urban, academic medical center. Methods: This single-institution retrospective study included patients with HPV negative HNSCC who underwent ctDNA testing during routine clinical care. The objective was to correlate ctDNA detectability and post-treatment changes with clinical outcomes. A personalized tumor-informed multiplex PCR next-generation sequencing assay was utilized for ctDNA detection. Demographic, clinical, and treatment variables were abstracted from medical records. Disease response was determined through radiographic and clinical assessments. Results: The study included 33 patients (median age 60 years; 70% male). The cohort was racially diverse: 33% Black, 24% Hispanic, 18% White, and 15% Asian. Primary sites included oral cavity (n=19), larynx (n=6), hypopharynx (n=3), and oropharynx (n=3). Most patients presented with advanced disease (Stage IVC, n=24; Stage IVB, n=6). Seven patients were excluded due to insufficient sample quality or incomplete documentation. Among the remaining patients, 80% (21/26) had detectable ctDNA. Serial testing was performed in seven patients. Two patients with initially negative tests developed positive results correlating with disease recurrence. Five patients had positive baseline testing; repeat testing after therapy showed decreased or undetectable levels. Of these, one had a significant response, two had stable disease, one had a mixed response, and one had disease progression despite ctDNA decrease. Conclusions: ctDNA may complement radiographic and clinical assessment in HNSCC by providing sensitive molecular response data. In this cohort, serial assays paralleled recurrence in some cases, though a post-treatment decrease did not always correlate with clear overall imaging response in minor percentage of cases. Further research is warranted to validate ctDNA utility in diverse HNSCC populations.
Ansari et al. (Thu,) studied this question.