The role of liquid biopsy in management of the neck with indeterminate response on post-treatment imaging following non- surgical management of oropharyngeal cancer

Introduction: This study aimed to determine if post-treatment HPV cell-free DNA (cfDNA) can assist in the decision-making process for salvage neck dissection in patients following non-surgical treatment of oropharyngeal squamous cell carcinoma (OPSCC) with a partial response in the neck on imaging at 12 weeks post-treatment.Methods: 86 patients who completed treatment were prospectively recruited through the regional multidisciplinary team (MDT). Treatment response was categorised as complete response (CR), partial response (PR) or progressive disease on 12-week post-treatment imaging. Pre-and post-treatment blood samples were assessed for HPV cfDNA through droplet digital PCR (ddPCR).Results: Eight patients had an isolated partial response in the neck. One (12.5%) had detectable HPV cfDNA (22.96 copies/ml) at-12 weeks post-treatment with positive disease on subsequent neck dissection (positive predictive value; PPV = 100%). Of the seven patients with undetectable HPV cfDNA, two patients had evidence of regional disease recurrence at 23.9 and 27.4 months respectively (negative predictive value; NPV = 71%).Conclusion: The detection of HPV cfDNA may help target salvage therapy in patients with a partial response in the neck. Follow-up studies in larger cohorts would be required to further validate the use of post-treatment HPV cfDNA in the management of OPSCC.(c) 2022 Elsevier Ltd, BASO -The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.