Clinical validity of TTMV-HPV DNA liquid biopsies for the diagnosis and surveillance of HPV-associated oropharyngeal carcinoma.

6060 Background: While there are several HPV biomarker assays, a commercially available assay evaluating tumor tissue modified viral DNA (TTMV-HPV DNA) (NavDx, Naveris Inc, Natick, MA) has shown impressive results in clinical trials and small cohort studies. Our aim was to establish the clinical efficacy of plasma TTMV-HPV DNA testing in the diagnosis and surveillance of HPV-associated OPSCC in a contemporary, real-world clinical setting. Methods: In this retrospective analysis, we evaluated the accuracy of the TTMV-HPV DNA assay in detecting HPVOPSCC in the diagnostic (pre-treatment) and surveillance phases of care between April 2020 and October 2022. For the diagnostic cohort, patients with OPSCC and at least one TTMV-HPV DNA measurement prior to initiation of primary therapy were included in the analysis. For the surveillance cohort, all TTMV-HPV DNA tests performed 3 months after completion of primary therapy for pathologically confirmed HPV-associated OPSCC were evaluated, regardless of pre-treatment TTMV-HPV DNA testing. Patients with suspected recurrence, but without pathologic confirmation, were excluded. HPV status was defined utilizing positive p16 staining on immunohistochemistry (93.2% diagnosis; 97.9% surveillance) or HPV polymerase chain reaction/in situ hybridization (79.6% diagnosis; 89.7% surveillance). Results: In the diagnostic cohort, 163 patients were included. The cohort included mostly men (87%) with median age 63, of which 93.3% had HPVOPSCC versus 6.7% had HPV negative OPSCC. The sensitivity in pre-treatment diagnosis was 91.5%; its specificity was 100%. In the surveillance cohort, 591 tests conducted in 290 patients were evaluated. 23 patients had pathologically confirmed recurrences. The assay demonstrated 79.2% sensitivity and 100% specificity in detecting the recurrences. Positive predictive value was 100% and negative predictive value was 98.2%. The median lead time from positive test to pathologic confirmation was 28 days, 6/18 (30%) had lead time >50 days (maximum 507 days). Conclusions: The commercially available NavDx TTMV-HPV DNA assay demonstrated 100% specificity, and therefore excellent positive predictive value, in both diagnosis and surveillance. However, the sensitivity was lower, 91.5% for the diagnosis cohort and 79.2% for the surveillance cohort, signifying that a negative value may require further work-up. Further studies will be required to determine the optimal timing of testing and how results should inform treatment decisions. [Table: see text]