ctDNA predicts recurrence and survival in stage I and II HPV-associated head and neck cancer patients treated with surgery.

Human papillomavirus-associated oropharyngeal squamous cell carcinomas (HPV+OPSCC) release circulating tumor HPV DNA (ctHPVDNA) into the blood which we, and others, have shown is an accurate real-time biomarker of disease status. In a prior prospective observational trial of 34 patients with AJCC 8 stage I-II HPV+OPSCC treated with surgery, we reported that ctHPVDNA was rapidly cleared within hours of surgery in patients who underwent complete cancer extirpation, yet remained elevated in those with macroscopic residual disease. The primary outcomes of this study were to assess 2-year OS and RFS between patients with and without molecular residual disease (MRD) following completion of treatment in this prospective cohort. MRD was defined as persistent elevation of ctHPVDNA at two consecutive time points, without clinical evidence of disease. The secondary outcomes were 2-year OS and RFS between patients with and without detectable MRD after surgery. We observed that patients with MRD after treatment completion were more likely to recur compared to patients without MRD, while there was no difference in recurrence rates between patients with MRD and without MRD on postoperative day 1. OS did not significantly differ between patients with MRD after surgery or treatment completion compared to patients without MRD; however, time to death was significantly different between the groups in both settings, suggesting that with a larger sample size OS would differ significantly between the groups or that the impact of MRD detection on survival is time dependent.