Prognostic Value of Combined Programmed Cell Death 1 Ligand and p16 Expression Predicting Responsiveness to Radiotherapy in Patients with Oropharyngeal Squamous Cell Carcinoma

Abstract

Background and Objectives This study examined the expressions of p16 and the programmedcell death 1 ligand (PD-L1) in patients with oropharyngeal cancer (OPC) treated withradiotherapy (RT) to identify the correlation between p16 and PD-L1 expression, and to examinethe prognostic significance of these markers for OPC patients receiving RT. Subjects and Method Forty-eight OPC patients diagnosed and treated at a tertiary referralhospital were enrolled in this retrospective analysis. Patients were initially treated with RT orchemoradiotherapy (CRT) with curative intent and completed the planned schedule. Expressionof p16 and PD-L1 by primary tumors was evaluated by immunohistochemistry, and resultswere interpreted separately and dichotomized according to outcome analyses. Results Of the 48 patients, 25 (52.1%) expressed p16 and 15 (31.3%) expressed PD-L1. Expressionof these markers showed a mutual positive correlation (p=0.046). Positive PD-L1 expressionwas associated with poor complete remission (CR) rates after RT (p=0.040). Positivep16 expression was associated with better recurrence-free survival (RFS) (p=0.004) but notoverall survival (OS) (p=0.192). PD-L1 expression showed no independent association withsurvival (p>0.05); however, PD-L1 expression tended toward poorer RFS, even in p16-positiveindividuals. Conclusion There was a positive correlation between the expression of p16 and PD-L1 inOPCs. PD-L1 expression was associated with poorer CR rates after RT or CRT. PD-L1 alonedid not show an association with RFS or OS, but when combined with p16, it tended towardpoorer RFS, even in p16-positive cases.