Postoperative Lymphatic Exudate is a Proximal Source of ctDNA and Detects Recurrence in HPV-negative Head and Neck Cancer

PurposeRelapse is a major cause of failure in human papillomavirus (HPV)-independent head and neck squamous cell carcinoma (HNSCC). Clinicopathologic criteria for adjuvant treatment remain imprecise and have not changed for decades. We investigated whether circulating tumor DNA (ctDNA) in lymphatic exudate collected via surgical drains ("lymph") 24-hours after surgery identified molecular residual disease (MRD) and compared its performance to time-matched plasma. Experimental DesignUsing an ultra-sensitive tumor-informed sequencing approach, tumor variants were called in lymph and plasma to classify patients as ctDNA-positive or ctDNA-negative, trained in an initial cohort of 36 patients and replicated in an independent cohort of 37 patients. Progression-free survival (PFS) was compared in ctDNA+ vs. ctDNA-patients. ResultsLymph identified MRD in two independent multi-site cohorts (initial cohort sensitivity = 76%, specificity = 63%, P = 0.01; replication cohort sensitivity = 65%, specificity = 70%, P = 0.04). Lymph performance was enhanced in locoregional relapse (sensitivity = 78%, specificity = 67%, P = 0.0004) and generalized to early-stage patients. Analysis of matched plasma collected at this early timepoint was not predictive of recurrence (sensitivity = 35%, specificity = 72%, P = 0.7). In patients with intermediate-risk pathology, lymph ctDNA was associated with recurrence (sensitivity = 88%, specificity = 67%, P = 0.0008), suggesting an opportunity for improved stratification of patients who may benefit from additional adjuvant treatment. ConclusionPostoperative lymph is a novel, proximal, and early source of MRD with the potential to introduce more precision into adjuvant therapy decision-making and improve outcomes, especially for intermediate-risk HPV-independent HNSCC patients. Translational RelevancePostoperative lymphatic exudate represents a proximal analyte for MRD detection in HPV-independent HNSCC designed specifically for use in the immediate post-surgical window when adjuvant therapy decisions must be made. Accurate MRD identification at this early timepoint has the potential to augment traditional pathology and personalize adjuvant treatment paradigms in HPV-independent HNSCC.