Abstract 3775: Liquid biopsy for therapy planning in clinically N0 head and neck cancer (LiC0HN) - A personalized cell-free tumor DNA analysis for patients with HNSCC

Abstract Introduction: Diagnosis and prognostic assessment as well as ultimate therapeutic success in treatments for patients with head and neck squamous cell carcinoma (HNSCC) requires that lymph node status is classified correctly. In patients where cervical lymph nodes are clinically not involved (cN0) the choice of appropriate therapy remains intensely debated. Biomarkers such as cell-free circulating tumor DNA (ctDNA) to improve accuracy of metastatic cervical lymph node detection may lead to a reduction in ineffective surgery in the form of neck dissection and thus optimize management of the cN0 neck. In the previous LIONESS study we have been able to show the potential of using personalized ctDNA detection as a marker of molecular residual disease following curative-intent treatment. Methods: We conducted a single-center prospective cohort study to investigate the optimal approach to identify ctDNA in patients with cN0 HNSCC. We recruited 75 patients as part of the LiC0HN study with stage I-IV HNSCC at a single University Hospital receiving primary surgical treatment with curative intent. Biosamples collected included serial tumor and lymph node tissue, plasma, buffy coat and dried blood spots (DBS). We had three aims (1) To investigate whether ctDNA detection using whole genome sequencing (WGS)-informed methods reflects lymph node metastasis preoperatively and surgical tumor clearance postoperatively (2) To explore detection of ctDNA in DBS using copy number alterations and (3) To identify epigenetic markers in the primary tumor and lymph node which may be useful to develop methylation-based ctDNA assays. WGS was performed on cell-free DNA from plasma and a subset of patients with DBS to a median depth of 10x and 5x respectively, as well as matching tumor and buffy coat DNA. We performed enzymatic library preparation for whole methylome sequencing on FFPE tissue (primary tumor and lymph node) from additional patients with HNSCC with or without lymph node metastasis (n=10 for each cohort). Results: In a subset of patients analyzed copy number alterations were identified in pre- and postoperative samples. Our analysis to identify differentially methylated biomarkers for cervical lymph node metastasis showed 24 differentially methylated regions of interest which were shared between the primary tumor and corresponding lymph node metastasis. In total 22 CpG blocks were differentially methylated in the same direction, including regions covering genes involved in cell-cell adhesion and metastasis. Analysis of plasma and DBS samples will be presented along with data from the full patient cohort. Conclusions: The use of ctDNA detection in surgically treated patients with HNSCC has significant potential to guide treatment decisions, including optimizing the use of surgical neck dissections, and improve disease outcome for patients. Citation Format: Susanne Flach, Arif Surani, Ze Zhou, Hui Zhao, Paulius Mennea, Fazlur Talukdar, Grainne McAndrew, Celina Greger, Christoph Walz, Philipp Jurmeister, Axel Lechner, Christoph Reichel, Olivier Gires, Martin Canis, Philipp Baumeister, Nitzan Rosenfeld, Amit Roshan. Liquid biopsy for therapy planning in clinically N0 head and neck cancer (LiC0HN) - A personalized cell-free tumor DNA analysis for patients with HNSCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3775.