Abstract A37: Analysis of inconcordance between p16, p53 immunohistochemistry, and HPV-PCR genotyping in tonsil cancer
Authors: Kim Geun-Jeon , Nam Inn-Chul , Kim Chung-Soo , Kim Min-Sik 
Published: September 2020

Abstract
Introduction: Subsequent epidemiologic studies have demonstrated a growing predominance of HPV infection in oropharyngeal squamous cell carcinomas (OSCC), particularly involving the tonsils. Detection of p16 overexpression is the most widely used test because it is the least expensive and the easiest to perform. However, this test has a sensitivity of 94% but an insufficient specificity of 82%. OSCC have been examined for other molecular markers including p53. Here, we investigated the prevalence of HPV and its relationship (especially for the inconcordance) with p16 and p53 in patients with OSCC.
Materials and Methods: The clinical and pathologic data of total 89 patients who underwent surgical management for squamous cell carcinoma (SCC) of tonsil from 2000 to 2016 with thirty-month minimum follow-up periods were reviewed. We evaluated for demographic, clinical history, survival rate, p16, p53, and HPV association.
Results: Among the 89 patients, 20 patients were excluded from p16 and HPV study, because they were incomplete test for study. So, we divided 69 patients into four groups: group 1, p16 positive and HPV positive (n=41, 59.4%); group 2, p16 negative and HPV negative (n=11, 15.9%); group 3, p16 positive and HPV negative (n=13, 18.8%); and group 4, p16 negative and HPV positive (n=4, 5.8%). There was significant difference in early T stage (T1 and 2) rate between group 1 and group 2 (90.2% vs. 36.3%, p=0.001), but not in 5-year overall survival (OS) rate (81.8% vs. 63.6%, p=0.127). Also, there was significant difference N positive rate between group 1 and group 3 (p=0.033), but not in 5-year overall survival (OS) rate (81.8% vs. 75%, p=0.479). Group 3 was also showed significant difference in early T stage rate from group 2 (90.2% vs. 76.9%, p=0.045). Group 4 showed no significant results with any group. For p53 and HPV study, we divided 89 patients into four groups: group 1, p53 negative and HPV positive (n=28, 31.4%); group 2, p53 negative and HPV negative (n=19, 21.3%); group 3, p53 positive and HPV positive (n=23, 25.8%); and group 4, p53 positive and HPV negative (n=19, 21.3%). There was significant difference in early T stage (T1 and 2) rate between group 1 and group 2 (p=0.029), but not in N positivity and 5-year overall survival (OS) rate. Also, there was no significant results with any group.
Discussion: We can analyze the influence of p16 according to HPV status through group 2 and group 3. The p16 positive groups showed high early T stage rate regardless of HPV status, but there no statistical difference in N stage and 5-year overall survival. We also estimated that the N positivity was determined by HPV status rather than p16 by comparing group 1 and group 3. In HPV and p53 results, high T 1/2 stage rate is thought to be the result of HPV status, and p53 status showed no significant effect on stage, survival, and recurrence.
Conclusion: The p16 test is insufficient when used alone to reliably confirm the viral origin of an OSCC. The combined use of these p16 and HPV tests would be more reliable but cannot eliminate all ambiguity.
Citation Format: Geun-Jeon Kim, Inn-Chul Nam, Chung-Soo Kim, Min-Sik Kim. Analysis of inconcordance between p16, p53 immunohistochemistry, and HPV-PCR genotyping in tonsil cancer [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr A37.