p16INK4 expression is of prognostic and predictive value in oropharyngeal cancers independent of human papillomavirus status: a Hungarian study

Head and neck cancer treatment protocols still lack well-established biomarkers of prognostic and predictive value. It is well known that human papillomavirus (HPV)-related and non-HPV-related oropharyngeal cancers are distinct entities concerning tumor biology and clinical outcome. However, there is an ongoing debate whether tumor suppressor p16(INK4) status alone or both p16(INK4) and HPV detection should be used in clinical settings. The aim of this study was to investigate p16(INK4)-immunolabelled and HPV-induced rates and determine their clinical significance in 110 primary head and neck squamous cell carcinomas. The expression of p16(INK4) protein was assessed with immunohistochemistry, while high-risk HPV detection was performed using DNA PCR method. p16(INK4) immunolabelling was detected in 17.3% of all tumor samples, and in 38.1% of oropharyngeal malignancies. Oropharyngeal, p16(INK4)-immunolabelled tumors showed an improved disease-specific survival compared to the non-p16(INK4)-immunolabelled group (median survival: 30.3 vs. 8.8 months, p < 0.001 with the log-rank test). Furthermore, 56% of p16(INK4)-immunolabelled cases were tested positive for HPV-DNA. The HPV-induced group presented better disease-specific survival compared to the non-HPV-induced cases (median survival: 25.9 vs. 9.5 months, p = 0.024 with the log-rank test). Improved response rates to neoadjuvant chemotherapy were observed both in p16(INK4)-immunolabelled and p16(INK4)-immunolabelled/ HPV DNA- containing groups (Fisher's exact test: p = 0.025 and p = 0.009). In conclusion, p16(INK4) immunohistochemistry proved to be a reliable and affordable tool for prognostic and predictive testing of head and neck squamous cell cancers. The p16(INK4) immunopositivity status alone was confirmed to be an equally precise indicator of clinical outcome as p16(INK4)/HPV DNA PCR double testing.