Multi-feature next-generation liquid biopsy for diagnosis and prognosis in HPV-associated head and neck cancer.

6064 Background: Human papillomavirus-associated head and neck squamous cell carcinoma (HPV+HNSCC) releases circulating tumor HPV DNA (ctHPVDNA) into the blood which is a highly accurate biomarker of disease status. Existing approaches based on droplet digital PCR (ddPCR) have limitations in sensitivity, genotype coverage, and do not annotate additional prognostic genomic features. In this study, we tested the diagnostic and prognostic performance of a custom HPV whole-genome next-generation sequencing (NGS) liquid biopsy, termed HPV-DeepSeek, at the time of diagnosis with HPV+HNSCC, compared to ctHPVDNA ddPCR, HPV serology, and clinical work-up. Methods: 304 participants (152 untreated HPV+HNSCC patients, 152 population-level controls) were prospectively enrolled in this single-center prospective cohort study. Plasma samples were analyzed using HPV-DeepSeek, a multiplexed serology assay, single-plex ddPCR, and a 5-genotype multiplexed ddPCR assay. We tested the hypothesis that HPV-DeepSeek would have the highest diagnostic accuracy. We secondarily examined the accuracy of HPV-DeepSeek for prognostic feature annotation including high-risk HPV16 single nucleotide polymorphisms (SNPs), integration events, and PIK3CA mutations. Results: Of 152 cases, 114 (75%) were AJCC stage 1 and 138/152 (91%) were oropharynx primary site cancers. The sensitivity (98.7%), specificity (98.7%), and diagnostic accuracy (0.974) of HPV-DeepSeek was superior (P<0.001) to singleplex ddPCR (94.2%, 98.6%, 0.928), multiplex ddPCR (90.6%, 96.3%, 0.869), HPV serology (86.4%, 96.3%, 0.827), and first attempt clinical diagnostic biopsy (78% sensitive). Utilizing HPV-DeepSeek, 8 different genotypes were detected. 4 patients were found to have multi-genotype infections. 137/152 cases were classified as HPV16, with A1 the most common sub-lineage (90/137). 21 of 137 HPV+HNSCC HPV16 cases (15%) displayed high risk SNPs. Head-to-head comparison of HPV SNP genotyping by HPV-DeepSeek, with the gold-standard tissue-based HPV whole genome sequencing assay, demonstrated 89% concordance in tissue and 85% in blood. The internal concordance rate for HPV-DeepSeek between tissue and blood was 91%. 48 of 152 cases (32%) had at least one viral integration event detected and 36 of 152 cases (24%) had a PIK3CA mutation detected by HPV-DeepSeek. Fragmentomic analysis demonstrated a mean ctHPVDNA fragment size of 148bp for ctHPVDNA versus 167bp for human cell free (cf)DNA from HPV+HNSCC patients and 168bp for control patient cfDNA. Baseline ctHPVDNA quantity was strongly correlated with viral integration status, T stage and N stage (P<0.001). Conclusions: HPV-DeepSeek has improved diagnostic accuracy relative to ddPCR, HPV serology and clinical work-up at the time of diagnosis and demonstrates detection of prognostic features including high-risk HPV16 SNPs, viral integration events, and PIK3CA mutations.