Liquid biopsy-based monitoring of disease status in patients with HPV-positive oropharyngeal carcinoma (OPSCC)

Introduction: The incidence of HPV-associated oropharyngeal carcinoma (HPV+ OPSCC) is increasing worldwide. In cases of tumor recurrence, distant metastases are often already present, which complicates curative tumor treatment. It is therefore of highly critical to collect molecular parameters to monitor the response of patients to therapy. Material/Method: The aim of this study is to establish an HPV-specific blood-based analysis (liquid biopsy) to enable both early diagnosis and monitoring of disease progression. To this end, our clinical biobank includes >1800 circulating tumor DNA (ct-DNA) samples from> 300 patients with HPV-associated OPSCC at the time of initial diagnosis, during tumor treatment, as part of clinical follow-up care, and in the event of tumor recurrence. Results: In a cohort of 434 longitudinally collected ctDNA samples from 53 patients with HPV+ OPSCC quantitative PCR (qPCR) and digital droplet PCR (ddPCR) was performed probing for E6 HPV-16 DNA sequences. In all cases, the HPV status was confirmed by p16-IHC, HPV16 DNA PCR for E6 and L1, and determination of the viral load in the tumor. There was a high concordance between qPCR- and ddPCR-based detection of HPV E6 (P<0.001), with ddPCR yielding higher sensitivity and specificity (>80%). HPV-16 ctDNA levels significantly correlated with tumor stage and tumor volume (P<0.05). In individual cases, a positive HPV ctDNA signal could be determined months before the diagnosis of tumor recurrence. Discussion: ddPCR-based quantification of ct-HPV16-E6 DNA in blood is a promising diagnostic method to monitor therapy response and tumor progression in patients with HPV+ OPSCC. Prospective clinical studies are warranted to clinically validate ct-HPV16-E6 DNA as a quantitative biomarker for therapeutic efficacy and longitudinal disease monitoring.