Combined Assessment of HPV and p16 Optimizes Clinical Decision-Making in Head and Neck Cancer of Unknown Primary.

BACKGROUND: Human papillomavirus-associated oropharyngeal squamous cell carcinoma (HPV+ OPSCC) is increasing in Sweden with implications for both the incidence and management of HPV+ head and neck cancer of unknown primary (HNCUP). In OPSCC, the combined presence of HPV DNA (HPV DNA+) and p16INK4a (p16+) overexpression has been shown to provide superior prognostic information compared with either marker alone. In this study, we therefore aimed to assess whether the prognostic impact of HPV DNA and p16 concordance/discordance in HNCUP mirrors that observed in OPSCC, within a high HPV-prevalent and low smoking population. METHODS: In this retrospective population-based cohort of 141 patients with HNCUP diagnosed at Karolinska University Hospital between 2000 and 2024, 128 had complete HPV DNA and p16 data and were included in analyses. RESULTS: Consistent with previous findings in OPSCC, combined assessment of HPV DNA and p16 provided superior prognostic stratification compared with either marker alone. Nevertheless, HPV DNA+ as a single marker showed a prognostic impact almost comparable to that of combined HPV DNA+/p16+ status, while p16+ alone, although associated with some prognostic value, was less informative. HPV DNA-negative disease was associated with poor prognosis irrespective of p16 status. CONCLUSIONS: The data suggest that combined assessment of HPV DNA and p16 is superior in HPV-associated HNCUP. However, in settings where a single test must be chosen, and especially in areas with high prevalence of HPV + OPSCC, HPV DNA is preferable to p16. Such a strategy could simplify diagnostic workflows while still enabling effective risk stratification and supporting tailored patient management.