Is immunohistochemical evaluation of p16 in oropharyngeal cancer enough to predict the HPV positivity?

Abstract

Aim

Our goal was to determine the expression levels of p16 in the cohort of the OPSCC patients and evaluation of the pathological and clinical differences between these two groups including patients’ survival.

Background

HPV infection is the main causative factor of oropharyngeal cancer (OPSCC). Identification of HPV status in OPSCC requires positive evaluation of viral DNA integration into host cell however, p16 accumulation in the proliferating cell layers has been accepted as an alternative marker for HPV infection.

Material and Methods

The IHC staining for p16 has been performed in tumor tissue from 382 OPSCC patients. The sample was considered positive based on more than 70% of carcinoma tissue showing strong and diffused nuclear and cytoplasmic immunostaining. The clinicopathological characteristics of the patients including site, age, gender, tumor grade, tumor stage, the nodal status, smoking and survival have been analyzed when comparing p16 positive and p16 negative tumors.

Results

Out of our cohort in 38.2% cases positive staining for p16 has been recorded. Our analysis did not indicate significant differences in the distribution of the p16 positive patients and age of the patients, stage of the disease. Among the patients who have presented with the N+ neck, there were significantly more p16 positive tumors than in the group with N0 neck (p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.0062). There was highly significant correlation between the expression of p16 and smoking (p[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.0001). The significant difference in survival (p[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.0001) with more favorable prognosis in the p16 positive group has been observed.

Conclusions

Overexpression of p16 is accepted as a surrogate diagnostic marker for detecting HPV infection in oropharyngeal cancer. However, one should remember about existence of the small subgroups of p16 positive but HPV negative tumors, with relatively worse prognosis. Immunostaining for p16, however useful on everyday basis, should be complemented with other techniques in terms of reliable identification of the HPV infection.