Added value of HPV-DNA in situ hybridization as an adjunct to p16 Immunohistochemistry in oropharyngeal squamous cell carcinoma.

Abstract

Background: Current guidelines recommend p16 immunohistochemistry (IHC) for testing human papillomavirus (HPV) in oropharyngeal squamous cell carcinoma (OPSCC). The need for additional HPV-DNA testing is debated.

Aims/objectives: We evaluated the prognostic value of HPV-DNA in situ hybridization (ISH) as an adjunct to p16.

Material and methods: A population-based cohort of 1,033 head and neck squamous cell carcinoma patients was used, to identify 124 OPSCC patients treated with a curative intent.

Results: Of the p16-positive patients, 17.9% did not show evidence for presence of HPV-DNA in ISH. Both p16 and HPV-DNA ISH were significant prognostic factors for overall survival (OS), disease-specific survival (DSS) and disease-free survival (DFS) when used independently. When combining information from p16 IHC and HPV-DNA ISH, survival of the p16+/ISH- discordant patients was intermediate compared to the p16+/ISH+ and p16-/ISH- groups. In the discordant group, smoking was a strong prognostic determinator, with non-smokers having an outstanding prognosis.

Conclusions and significance: Both p16 IHC and HPV-DNA ISH perform well as separate prognostic biomarkers for OS, DSS, and DFS on a population level. However, a discordant group does exist. Limiting HPV-DNA testing for p16-positive patients who smoke by the time of diagnosis may be a cost-efficient and justified solution.