Background: p16 has been indicated as a suitable surrogate biomarker of HPV infection. The prognosis of p16-positive oropharynx tumors (OTs) of squamous cell carcinoma (SCC) histology is better than that of p16-negative tumors.
Methods: We analyzed 209 samples of head and neck SCC to establish a predictive cutoff for p16 and determine the role of p16 positivity in OTs versus non-OTs. We compared the outcomes of tumors harboring any percentage of p16-positive cells (≥1%) with those of p16-negative OTs. We then considered 3 cutoffs (10%, 50% and 70% positive cells) to evaluate the outcome of OTs/non-OTs with similar p16 expression and p16-positive versus p16-negative tumors stratified by patient age.
Results: p16-negative tumors among OTs and non-OTs were 29% and 49%, respectively (p = 0.0054). The cumulative distribution showed that the positive values were located around 2 focus points: 2% and 96%. Subgroup analysis showed that only OTs occurred in young patients (aged <65 years) and that there was a ≥70% gain in survival in cases with p16-positive cells.
Conclusions: p16 positivity influences outcome only in young patients and OTs (p = 0.048).