To Örebro University

OBJECTIVES: HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) and head and neck carcinoma of unknown primary (HNCUP) are increasing. Despite good prognosis, recurrence rates range from 10% to 25%. Surveillance with clinical controls and imaging is not always reliable. Circulating tumour human papillomavirus DNA (ctHPV-DNA) has emerged as a potential biomarker for treatment evaluation and detection of recurrence. We aimed to investigate the correlation between ctHPV-DNA in HPV+ OPSCC/HNCUP and radiologic tumour burden. Additionally, we sought to assess whether ctHPV-DNA could serve as a tool in treatment evaluation.

DESIGN: A prospective observational cohort study.

SETTING: This multicenter study involved three otolaryngology units located in central Sweden. We utilised HPV genotype-specific assays for droplet digital PCR (ddPCR) to detect ctHPV-DNA in plasma at diagnosis and follow-up. ctHPV-DNA levels were correlated to radiological tumour burden and radiological response using the Kendall Rank correlation coefficient and the Kruskal-Wallis test.

PARTICIPANTS: Patients with HPV+ OPSCC/HNCUP undergoing definitive (chemo)radiotherapy and enrolled in the CIRCOS study. RESULTS: Out of 54 patients, 51 were eligible for analyses. At baseline, ctHPV-DNA was detectable in 88%. A majority of patients with a favourable radiological evaluation according to RECIST had a corresponding undetectable ctHPV-DNA at follow-up. The levels of ctHPV-DNA at baseline correlated with total tumour volume and nodal volume (rτ = 0.39, p < 0.01, respectively rτ = 0.26, p < 0.01).

CONCLUSION: ctHPV-DNA shows correlation with tumour burden. This study strengthens the role of ctHPV-DNA as a promising biomarker for treatment evaluation in HPV-related OPC/HNCUP. With further research on serial plasma sampling, ctHPV-DNA could complement radiological treatment evaluation in HPV+ OPSCC/HNCUP.

TRIAL REGISTRATION: NCT05904327 [ClinicalTrials.gov].

BACKGROUND: Human papillomavirus (HPV) has emerged as a significant contributor to cancer incidence globally, particularly in the context of oropharyngeal squamous cell carcinoma (OPSCC) and cancer of unknown primary (HNCUP). This study aimed to develop and validate droplet digital PCR (ddPCR) assays for the detection of circulating tumor HPV DNA (ctHPV-DNA) in plasma, focusing on high-risk HPV genotypes associated with these cancers.

METHODS: ddPCR assays for HPV16, 18, 33, 35, 56, and 59 were developed and tested using gBlocks, HPV cell-free DNA, fragmented tumor HPV+ DNA, and plasma samples from patients with HPV+ OPSCC (n = 110) and HNCUP (n = 9).

RESULTS: Assays demonstrated robust technical sensitivity across all tested HPV genotypes. Clinical application of the assays on a cohort of patients with HPV+ OPSCC and HNCUP revealed high sensitivity (91.6%) and wide variability in ctHPV-DNA levels. Analyses revealed correlations between ctHPV-DNA levels and TNM stage and tumor viral load. The association between ctHPV-DNA and tumor viral load persisted even after adjusting for TNM stage. At posttreatment, 72.5% of samples had reached undetectable ctHPV-DNA levels. Having detectable ctHPV-DNA posttreatment was associated with a higher ctHPV-DNA level at diagnosis and higher viral load at diagnosis.

CONCLUSION: The findings underscore the potential of ctHPV-DNA as a biomarker for monitoring HPV+ cancers and offer insights into tumor dynamics. Implementation of these assays in clinical practice could enhance no-invasive treatment monitoring and recurrence detection in HPV-associated cancers.

CLINICAL TRIALS: NCT05904327.