PURPOSE: Human papillomavirus (HPV) is a significant cause of cervical cancer. We hypothesized that detecting viral cell-free HPV DNA (cfDNA) before, during, and after chemoradiation (chemoRT) could provide insights into disease extent, clinical staging, and treatment response. EXPERIMENTAL DESIGN: A total of 66 patients with locally advanced cervical cancer were enrolled between 2017 and 2023, with 49 receiving standard-of-care treatment and 17 participating in a clinical trial combining a therapeutic HPV vaccine (PDS0101
IMMUNOCERV). Plasma was collected at baseline, weeks 1, 3, and 5 of chemoRT, and 3 to 4 months after chemoRT. HPV cfDNA was quantified using droplet digital PCR targeting the HPV E6/E7 oncogenes of 13 high-risk types. MRI was performed at baseline and before brachytherapy. RESULTS: The median follow-up was 23 months, with recurrence-free survival (RFS) of 78.4% at 2 years. Baseline nodal disease extent correlated with HPV cfDNA levels. HPV cfDNA levels peaked in week 1 of radiation and decreased through treatment. Patients receiving the PDS0101 vaccine had a higher rate of undetectable HPV type 16 cfDNA compared with those who received standard-of-care therapy. HPV cfDNA clearance correlated with better 2-year RFS (92.9% vs. 30%, log-rank
P = 0.0067). The strongest predictor of RFS was HPV cfDNA clearance in follow-up achieving a concordance index score of 0.83, which improved when combined with MRI response (concordance index, 0.88). CONCLUSIONS: HPV cfDNA levels change dynamically during chemoRT. HPV cfDNA levels at follow-up predict RFS, and delivery of therapeutic HPV vaccine with chemoRT was linked to rapid HPV cfDNA decline. Monitoring HPV cfDNA during and after chemoRT may guide tailoring of personalized treatment.