The Prognostic Significance of p16 and its Role as a Surrogate Marker for Human Papilloma Virus in Oral Squamous Cell Carcinoma: An Analysis of 281 Cases

Abstract

Background/Aim: This study analyzed the expression of p16 in a large cohort of patients suffering from oral squamous cell carcinoma (OSCC) who received initial surgical therapy in order to evaluate the prognostic significance of p16 expression and to analyze its value as a surrogate marker to determine human papilloma virus (HPV) status. Materials and Methods: Immunohistochemical staining of p16 was performed on tissue microarrays. Different expression levels of p16 (>25%; >50%; ≥70%) with a moderate to strong intensity were correlated with the clinical outcome. HPV DNA was analyzed by polymerase chain reaction (PCR). Results: A total of 281 patients were included in this study. The p16 expression obtained using the abovementioned three different cutoffs did not significantly influence 5-year overall survival (OS) (p=0.23; p=0.45; p=0.23) nor recurrence-free survival (RFS) (p=0.79; p=0.45; p=0.142). In univariate Cox regression analysis, the p16 expression level was not a risk factor for OS (HR=0.637; 95%CI=0.271-1.5; p=0.300) and RFS (HR=0.74; 95%CI=0.339-1.61; p=0.449). A total of 17 patients (6.0%) were p16 positive with a cutoff ≥70%. HPV DNA was found in 4/11 of these cases by PCR, resulting in a positive predictive value of 0.36. In patients receiving adjuvant radio(chemo)therapy, a significantly (p=0.042) longer OS was observed in patients with p16 expression greater than 25% vs. ≤25%. Conclusion: In comparison with OPSCC, (strong) p16 positivity is rare in OSCC; however, in patients receiving primary surgery with adjuvant radio(chemo)therapy, p16 expression is associated with a higher survival rate. In conjunction with prior studies, p16 does not seem to be a reliable surrogate marker for HPV infection in OSCC.