(A523) Circulating Tumor DNA for Surveillance of HPV+ Oropharynx Cancer in Rural and Underserved Settings

Introduction: Surveillance is critical after definitive therapy for oropharyngeal squamous cell carcinoma (OPSCC). NCCN guidelines currently recommend a minimum of nine, and up to 24, visits in the first five years of standard surveillance without recurrence. Circulating tumor DNA (ctDNA) is a quantitative biomarker for HPV circulating tumor DNA with a variety of emerging applications in HPV+ OPSCC which may be used as an adjunct tool for surveillance in rural settings.

Methods: At a single institution between January 2021 – November 2023, ctDNA was measured via NavDx ® blood collections for patients with HPV + OPSCC undergoing definitive treatment including surgery +/- adjuvant radiotherapy/chemoradiotherapy or definitive chemoradiation. ctDNA was measured at varying time points before and after treatment.

Results: 168 patients were identified with HPV+ OPSCC 95/168 (56.5%) patients living in rural communities, defined by a living in a city with a population of less than 50,000. They traveled a median of 142 miles each way for a median time of 150 minutes. 91/95 (96%) patients had at least one ctDNA test collected post treatment, and 9/91 (9.9%) of these had positive ctDNA levels after treatment, thus initiating investigation for residual disease or recurrence. 4/9 patients had known residual disease on PET-CT, and two had ctDNA levels measured prior to initiating adjuvant radiotherapy. One patient had no clinical evidence of recurrence on exam, but a positive ctDNA leading to a PET-CT, which revealed recurrent disease. 2/9 patients had clinical suspicion for recurrence on exam and same-day ctDNA was positive.

Conclusions: The majority of patients had negative ctDNA levels collected during post-treatment surveillance visits and no patients in our cohort had proven residual or recurrent disease with concurrent negative ctDNA levels. While in-person evaluations will always be critical in monitoring for recurrence, incorporating virtual visits with concurrent ctDNA levels in low risk patients may be a novel surveillance options for patients living in rural settings and improve overall adherence given decreased travel burden.