Abstract B018: Plasma-based circulating tumor tissue modified viral (TTMV)-HPV DNA for detection of recurrent HPV-driven anal cancer

Abstract Purpose: Squamous cell carcinoma of the anus (SCCA) is primarily driven by human papillomavirus (HPV) infection. Up to 30% of patients experience recurrence, necessitating improved surveillance strategies. Liquid biopsies have shown promise as a tool in oncology. This study investigates the clinical performance of circulating tumor tissue modified viral (TTMV)- HPV DNA in the post-treatment surveillance of SCCA. Patients and methods: This central IRB-approved retrospective cohort study included 117 patients diagnosed with HPV-driven SCCA from seven U.S. centers who had ≥1 TTMV-HPV DNA tests (NavDx®, Naveris, Inc., Waltham, MA) performed between March 2020 and June 2024. TTMV-HPV DNA for HPV subtypes 16, 18, 31, 33, and 35 were analyzed using droplet digital PCR. The diagnostic accuracy of TTMV-HPV DNA was evaluated by comparing test results with clinical evidence of SCCA recurrence determined through anoscopy, radiology, and/or tissue biopsy. Recurrence is defined as either a positive biopsy or subsequent salvage therapy. Results: Patients were primarily female (73%) with a median age 63 years. Median follow-up after initial treatment was 19 months. Forty-seven patients (40%) had pretreatment TTMV-HPV DNA testing, with a baseline detectability of 85.1% (40/47, 95% CI: 74.9–95.3). Of these, 24 were re-tested within 3 months post-treatment and 18 had undetectable TTMV-HPV DNA (75%). Those patients whose scores became undetectable had significantly longer recurrence-free survival than those whose scores remained detectable (log-rank test, p=0.01). One hundred and four patients (89%) underwent post-treatment testing, of which 91 provided relevant data for the analysis. Of these 91 patients, 27 (29.7%) experienced recurrence. Post-treatment testing demonstrated a per- patient sensitivity of 85.7% (24/28, 95% CI: 72.8-98.7). Of four patients with a false negative test, only one had biopsy-confirmed recurrence, whereas the remaining recurrences were not biopsied prior to starting salvage treatment. The positive predictive value of a single positive test was 97.6% (40/41; 95% CI: 92.8–100.0). One patient remains in active follow-up. Of the true positive post-treatment tests, 58% (14/24) predicted recurrence before clinical detection, with a median lead time of 59 days (range: 10–536). There were 141 negative post-treatment tests across 66 patients. This yielded a per-test specificity and negative predictive value of 99.3% (136/137, 95% CI: 97.8-100.0) and 97.2% (136/140, 95% CI: 94.9-99.9), respectively. Indeterminate TTMV-HPV DNA tests were rare (5/268,1.9%). However, clinically indeterminate findings (CIFs) were common, with 141 post-treatment CIFs identified across 52/117 patients (44.4%). TTMV-HPV DNA testing was able to correctly predict recurrence status in 94.3% of CIF cases. Conclusion: TTMV-HPV DNA testing is a sensitive and specific surveillance method for detecting early recurrence of HPV-driven SCCA. Citation Format: Shane Lloyd, Rafi Kabarriti, James Jabalee, Tyler Slater, Corbin Jacobs, Sean Inocencio, Michael Rutenberg, Chance Matthiesen, Kasha Neff, Gene-Fu F Liu, Tiffany M Juarez, Catherine DV Fitz, Stanley Liauw. Plasma-based circulating tumor tissue modified viral (TTMV)-HPV DNA for detection of recurrent HPV-driven anal cancer [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 B018.