Abstract 961: Detection of minimal residual disease in lymph predicts recurrence in HPV-negative head and neck cancer patients

Abstract Background: Locoregional cancer relapse remains a major cause of failure in head and neck squamous cell carcinoma (HNSCC), particularly for HPV-negative patients whose 2-year locoregional failure rate is up to 50%. There is unmet need for an accurate diagnostic test that predicts risk of recurrence prior to adjuvant therapy selection. We present a novel proximal assay for minimal residual disease (MRD) profiled in lymphatic exudate collected via surgical drains (“lymph”). Methods: Lymph, plasma, and blood were collected from 46 HPV-negative HNSCC patients postoperatively at 24 hours along with resected tumor. Cell-free DNA was extracted from lymph and plasma and sequenced using the TruSeq Oncology 500 panel to a depth of 100 million reads. Somatic mutations were identified by exome sequencing (200x) tumor and blood. Five patients had 2 mutations in tumor and were excluded. Two patients were censored due to lack of clinical data, yielding 18 patients with disease recurrence (REC) and 21 with no evidence of disease (NED) with 1 year of follow-up. Tumor-specific variants were force-called in lymph and plasma using a custom pipeline. Patients were considered MRD positive if the mean variant allele fraction (mVAF) was greater than 0. 015% (the estimated limit of detection). The Kaplan-Meier (KM) estimator with log-rank test and Cox proportional-hazards model were used for survival analyses. Logistic regression model was performed with 5-fold cross-validation. Results: KM survival analyses showed lymph accurately predicts recurrence (sensitivity (SN) = 78%, specificity (SP) = 67%; p = 0. 003, Hazard ratio (HR) = 4. 7), while plasma was not significant (p = 0. 92) at this postoperative timepoint. Performance was enhanced for locoregional relapse (SN = 92%, SP = 67%; p = 0. 001, HR = 13. 9. N=33). We also observed accurate recurrence prediction (SN = 83%, SP = 69%, p = 0. 03, HR = 7. 7) in the 19 N0 patients (node-negative by pathology). Lymph MRD outperformed individual pathology features (extranodal extension, perineural invasion, lymphovascular invasion, and nodal disease status) for recurrence prediction (HR = 3. 4, 0. 88, 2. 5, 2. 4, respectively). A logistic regression model combining lymph MRD with these 4 high-risk pathologic features showed superior performance over lymph alone or pathology alone (SN = 89%, SP = 67%; p = 0. 0007, HR = 8. 6). Conclusions: ctDNA analysis of lymph from surgical drains represents a novel proximal MRD approach in HPV-negative HNSCC. Postoperative lymph significantly outperforms plasma for prediction of recurrence, particularly in patients with locoregional relapse. Accurate MRD identification in patients with lower risk pathologic features suggests that lymph MRD testing has potential to augment traditional pathology and provide more personalized adjuvant treatment decision-making in patients with HPV-negative HNSCC. Citation Format: Wendy Winckler, Zhuosheng Gu, Damion Whitfield, Noah Earland, Adam Harmon, Megan Long, Peter Harris, Zhongping Xu, Ricardo Ramirez, Sophie Gerndt, Maciej Pacula, Marra S. Francis, Jose P. Zevallos, Aadel A. Chaudhuri. Detection of minimal residual disease in lymph predicts recurrence in HPV-negative head and neck cancer patients abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 961.