p16 overexpression and Rb loss correlate with high-risk HPV infection in oropharyngeal squamous cell carcinoma

Aims p16 is a sensitive surrogate marker for transcriptionally active high-risk human papillomavirus (HR-HPV) infection in oropharyngeal squamous cell carcinoma (OPSCC), but it is not sufficient in all clinical settings. Methods and results We examined the p16 and Rb expression status in 177 OPSCC cases by immunohistochemistry and the presence of transcriptionally active HR-HPV infection by mRNA in-situ hybridisation. The 177 cases were divided into p16(+)/HPV+ (n = 105, 59.3%), p16(+)/HPV- (n = 8, 4.5%) and p16(-)/HPV- (n = 64, 36.2%) groups. The p16(+)/HPV- and p16(-)/HPV- groups had a trend towards worse overall survival (OS) or significantly worse OS than the p16(+)/HPV+ group (n = 105) (P = 0.0610, P = 0.0004, respectively). We divided the Rb status into preserved expression (> 90%, n = 68), partial loss (PL) (10-90%, n = 97) and complete loss (CL) (< 10%, n = 12). Among the HPV-positive cases (n = 105), the Rb pattern was typically PL (n = 97, 92.4%) and rarely CL (n = 8, 7.6%), but never preserved expression (0%). In contrast, among the HPV-negative cases (n = 72), the Rb pattern was typically preserved expression (n = 68, 94.4%) and rarely CL (n = 4, 5.6%), but never PL (0%). Compared to p16 alone, the combination of p16 overexpression and Rb-PL/CL showed equally excellent sensitivity (each 100%) and improved specificity (97.2 versus 88.9%) and positive predictive values (98.1 versus 92.9%). Conclusions These results suggest that the combined use of p16 and Rb immunohistochemistry could be a reliable, cost-effective method to predict HR-HPV infection in OPSCCs; however, HPV specific testing is necessary on inconclusive cases. We propose a diagnostic algorithm for practical use of these markers.