Personalized cell-free tumor DNA analysis for patients with HNSCC: Liquid biopsy for minimal residual disease detection in head and neck squamous cell carcinoma (LIONESS).

3010 Background: Early relapse and development of metastatic disease are some of the primary reasons for the poor prognosis of patients with head and neck squamous cell carcinoma (HNSCC). We conducted LIONESS, a single-center prospective cohort study to assess ctDNA in plasma and saliva from 76 patients with HNSCC receiving primary surgery with curative intent. Our objectives were to determine whether postoperative ctDNA detection can act as a biomarker for surgical tumor clearance and detection of molecular residual disease (MRD) and to evaluate the potential of tumor-informed ctDNA analysis for early molecular-level detection of relapse or prior to clinically confirmed recurrence. Methods: Plasma and saliva samples from 76 HNSCC patients (37% stage I/II, 63% stage III/IV; 93% p16-negative) were collected pre- and postoperatively and during clinical follow-up. Whole exome sequencing was performed on FFPE tumor tissue. Tumor-specific variants for personalized assay design (RaDaR, NeoGenomics Laboratories) were selected and used in the analysis of serial samples for evidence of MRD. ctDNA levels were correlated to tumor volumes from staging CT, as well as pathological and other clinical parameters. Results: 617 longitudinal plasma and 128 saliva samples were collected pre- and postoperatively and during clinical follow-up (median follow-up time of 805 days). In plasma, ctDNA was detected at a median estimated variant allele frequency (eVAF) of 0.036% (0.000327% - 18.43%). 34% of positive samples had ctDNA levels detected at an eVAF of ≤0.01%. Increased plasma ctDNA levels were detected postoperatively in 96% of cases with confirmed clinical recurrences (21/22) with a median lead time of 160 days (6 – 763 days). Of the remaining 54 patients with no clinically confirmed relapse, ctDNA was detected immediately postop in 7 of them. In 5 patients, adjuvant therapy resulted in persistent ctDNA clearance, while 2 patients are deceased. ctDNA was also detected in baseline saliva samples from patients with HNSCC of various anatomical locations with a 74% overlap with the corresponding plasma ctDNA profiles. There was a strong linear correlation between larger tumor volumes and higher eVAF and a trend towards higher eVAF in cases with regional and distant recurrences in comparison to local relapse. Pathological tumor stage and lymph node involvement were both strongly correlated with preoperative ctDNA shedding. Conclusions: The use of ctDNA detection in surgically treated patients with HNSCC has significant potential to guide treatment decisions, improve disease outcome and potentially spare patients unnecessary, partially invasive interventions during clinical follow-up. Our work demonstrates the feasibility of tumor-informed ctDNA assays for detection of MRD postoperatively and for monitoring for early detection of relapse.