Aim: To test for human papillomavirus (HPV) DNA in material obtained from p16INK4a (p16) immunohistochemistry (IHC) stained slides of formalin-fixed paraffin-embedded (FFPE) tumor biopsies.
Background: HPV is a favorable prognostic factor in oropharyngeal squamous cell carcinoma (OSCC), where tonsillar and base of tongue squamous cell carcinoma (TSCC and BOTSCC) dominate. Hence. HPV DNA testing as a predictive marker is desirable even when FFPE material is unavailable. Glass slides with p16 staining, often used as a surrogate marker for HPV, are however generally available. Furthermore, the combination of HPV DNA and p16 positivity is established as being better than testing for HPV DNA, or p16 alone, and almost equivalent as testing for E6 and E7 mRNA for determining HPV driven OSCC. Presence of HPV DNA was therefore examined in cells from glass slides previously stained for p16.
Materials and methods: DNA extracted from cells scraped off glass slides from 23 TSCC; 24 BOTSCC and 50 cancers of unknown primary (CUP) of the head and neck, with known HPV DNA and p16 status was tested for presence of HPV by a bead-based multiplex assay.
Results: DNA was obtained from 95.9% of the TSCC/BOTSCC/CUP slides and exhibited 93.5% (87/93) concordance with the HPV DNA status of the original FFPEs, with 38/42 (90.5%) of the originally HPV DNA positive/p16 positive remaining HPV DNA positive and all HPV DNA negative samples staying negative.
Conclusion: A 93.5% concordance was obtained between the HPV DNA status of the original FFPEs and DNA obtained from p16 stained glass slides. Of the HPV DNA positive IHC samples 38/38 100% were derived from HPV DNA positive/p16 positive FFPE biopsies, while all HPV DNA negative samples stayed HPV-negative. This approach allows for safer identification of HPV-positive tumors, and useful for following patients with HPV-positive tumors in retrospective studies and for future decision-making.
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