Abstract A007: Transient elevation of ctHPVDNA in human papilloma virus-mediated oropharynx squamous cell carcinoma patients following diagnostic surgical procedures

Abstract

Abstract Background: Circulating tumor DNA (ctDNA) is now widely used across a variety of malignancies as a viable “liquid biopsy” method, with applications in early detection, treatment response evaluation, prognostication, and recurrence monitoring. Recently, ctDNA derived from the tumor-integrated HPV (ctHPVDNA) has borne promising results in HPV-associated cancers, including HPV+ oropharyngeal squamous cell carcinoma (OPSCC). Studies indicate that undetectable ctHPVDNA after complete surgical excision in HPV+ OPSCC corresponds with improved prognosis. However, ctHPVDNA kinetics after diagnostic procedures such as transoral robotic surgery (TORS) in head neck squamous cell carcinoma from an unknown primary (HNSCCUP) or unknown primary has not been extensively studied. The purpose of this study is to show an unexpected trend in NavDx levels following these procedures. Methods: Patients undergoing TORS at Stanford University (September 2023 and August 2024) were prospectively screened and enrolled. A commercially available ctHPVDNA assay (NavDx) was collected at baseline, immediate postoperative (24-48 hours), 7-14 days following surgery, 3 months post- treatment and every 3 months thereafter up to 12 months. Results: Eight patients presented with HNSCCUP, 87.5% (7/8) had detectable baseline ctHPVDNA levels ranging from 2 to 1237. 75% (6/8) of the patients were confirmed p16+ by immunohistochemistry (IHC), while 25% (2/8) tested HPV+ by in situ hybridization (ISH). Diagnostic TORS was performed in 75% (6/8), while 25% (2/8) underwent direct laryngoscopy, with all primary tumors found in the oropharynx, 100% (8/8). Notably, 85.7% (6/7) of patients showed an unexpected elevation in total tumor mutational volume (TTMV) scores post-diagnostic procedure compared to baseline, with ctHPVDNA levels ranging from 30 to 2466, including one case where levels nearly quintupled. One patient had no post-diagnostic procedure TTMV score due to a negative baseline. However, in one other case, there was a negative post-procedure level. Among those with elevated post ctHPVDNA, 71.4% (5/7) underwent complete TORS excision, resulting in decreased postoperative ctHPVDNA levels in all patients, consistent with recent studies. Conclusion: This study provides insight that diagnostic procedures, such as TORS or direct laryngoscopy, in patients with p16+ HPV-mediated oropharyngeal cancer may lead to transient and unexpected elevations in ctHPVDNA levels, measured by TTMV scores. Although most patients showed a subsequent decrease in ctHPVDNA levels following a complete tumor resection, the observed post-diagnostic elevation emphasizes the importance of considering the timing of ctHPVDNA measurements. These findings suggest surgical manipulation may temporarily influence ctHPVDNA kinetics that could impact clinical decision-making and postoperative monitoring. Further research is needed to understand the implications of these transient elevations and optimizing the timing of ctHPVDNA assessments in clinical practice. Citation Format: Hlu Vang, Joanne Soo, Nikita Bedi, Andrea Garofalo, Michelle M Chen, Andrey Finegersh, Floyd Christopher Holsinger. Transient elevation of ctHPVDNA in human papilloma virus-mediated oropharynx squamous cell carcinoma patients following diagnostic surgical procedures [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A007.