ARTICLE ABSTRACT
Purpose: To evaluate the accuracy of cell-free human papillomavirus-DNA (cfHPV-DNA) measurements in liquid biopsies in predicting disease in HPV+/p16+ oropharyngeal squamous cell carcinoma (OPSCC) patients. Experimental Design: This is a prospective cohort study. Plasma samples were collected before treatment, and serially after curative intended therapy at follow-up visits 2 weeks, and 6, 9, 12, 18, 24, and 30 months after treatment. A Droplet Digital (dd)PCR assay comprising eight HPV genotypes was used. HPV genotypes found in plasma and tumour tissue were compared. We correlated biopsy- or imaging-verified tumour progression to cfHPV-DNA in follow-up samples. Results: We enrolled 72 HPV+/p16+ OPSCC patients. Baseline sensitivity for cfHPV-DNA detection was 97.2% (95% CI 90.3%–99.6). CfHPV-DNA copy number/millilitre plasma correlated with tumour stage. We found a 100% concordance between HPV genotype in tumour tissue and plasma. Fifty-four patients were followed with serial blood samples for a median of 19.7 months (Interquartile Range: 13.5–25.5 months). Forty-one patients had undetectable plasma cfHPV-DNA in all follow-up samples, and none developed recurrences. Thirteen patients were classified as cfHPV-DNA positive in a follow-up plasma sample. Of these, five patients developed a recurrence, and three had residual cancer. It was possible to detect cfHPV-DNA in plasma 97–166 days prior to the proven recurrence. Conclusion: Our study, comprising the largest study of HPV+/p16+ OPSCC patients, using an ultrasensitive multiplex HPV gene panel, revealed a high sensitivity of cfHPV-DNA detection in the liquid biopsies. We recommend serial plasma HPV samples for clinical monitoring of HPV+/p16+ OPSCC patients.
