Detection of recurrence of HPV-driven oropharyngeal cancer by HPV cell-free DNA.

The incidence of oropharyngeal cancer (OPC) driven by human papillomavirus (HPV) is increasing in high-income countries. Recurrent tumors remain a major cause of HPV-OPC mortality, yet reliable biomarkers for post-treatment monitoring are lacking. This study evaluated HPV cell-free DNA (cfDNA) from blood plasma as a monitoring biomarker for the detection of HPV-OPC recurrence. Blood plasma from 59 OPC patients was collected at diagnosis and during follow-up. HPV cfDNA was quantified using a multiplex digital PCR assay targeting HPV16 and seven other high-risk types. Tumor HPV status was confirmed by p16INK4A immunohistochemistry, HPV DNA PCR, and E6 serology. At diagnosis, HPV cfDNA was detected with 95% sensitivity (36/38; 95% CI 82-99%) and 95% specificity (19/20; 95% CI 75-100%). For 24 HPV-OPC patients, follow-up samples were available (median follow-up 1.5 years), with four patients experiencing recurrence or persistence of HPV-OPC. In two patients, HPV cfDNA detection after initial clearance preceded clinical recurrence by 3 and 8 months, respectively. The third patient experienced recurrence 7 months after collection of the last blood sample, which was HPV cfDNA-negative. The fourth patient had persistent disease without HPV cfDNA detection. HPV cfDNA positivity after therapy had a positive predictive value of 75% for HPV-OPC recurrence within one year on a per-test basis. HPV cfDNA has been shown to have great potential as a minimally invasive monitoring biomarker for HPV-OPC surveillance. Monitoring HPV cfDNA levels may identify patients at risk of recurrence early, thereby potentially facilitating timely intervention. Studies with more participants are needed to establish a solid evidence base for surveillance protocols that incorporate HPV cfDNA.