Significance of p16 expression in head and neck cancer patients treated with radiotherapy and cetuximab

Abstract

HPV-infection, p16 positivity, and EGFR expression have been correlated with favorable responses of head and neck cancer patients treated with radiotherapy (RT) with or without chemotherapy. However, a possible correlation of HPV/p16 and EGFR status on the effect of RT in combination with cetuximab has not been sufficiently investigated. We analyzed tumor samples for p16 and EGFR expression and correlated these variables with treatment outcome. Cox-proportional-hazard regression models were applied to compare the risk of death among patients stratified according to risk factors. Survival was estimated by the Kaplan-Meier method. Results were compared with an institutional historical control group treated without cetuximab and with published data. Expression of p16 was predominantly found in oropharyngeal squamous cell cancer patients (OPSCC; 36.6% positivity; 92% of all cases), while EGFR was expressed at high levels in all tumor subsites (82%). p16 expression was associated with improved overall survival in irradiated OPSCC patients (2-year overall survival of 80% in p16-positive vs. 33% overall survival in p16-negative patients). In a multivariable analysis covering all tumor sites, nodal stage (> N2a vs. ≤ N2a) and tumor site (OPSSC vs. non-OPSCC) had an impact on overall survival. Our results show that p16 positivity is associated with a favorable outcome in OPSCC patients treated with RT and cetuximab.