Prognostic Significance of PD-L1+ and CD8+ Immune Cells in HPV+ Oropharyngeal Squamous Cell Carcinoma

Assessment of CD8+ cell infiltration and PD-L1 expression on intratumoral immune cells identified a subgroup of HPV+ OPSCC patients with excellent clinical outcomes. Immunophenotyping tumors provided prognostic information beyond that provided by existing TNM-based staging systems. Human papilloma virus–positive oropharyngeal squamous cell carcinoma (HPV+ OPSCC) represents a distinct subgroup of head and neck cancers associated with clinical outcomes that are not accurately categorized by existing tumor–node–metastasis-based staging methods. Given the significant impact of immune parameters, such as tumor-infiltrating lymphocytes (TIL) in many cancers, we sought to determine if immunophenotyping tumors can improve categorization of HPV+ OPSCCs for prognostic purposes. In a cohort of 190 patients with HPV+ OPSCC, we quantified and determined the localization of CD8+ TILs, as well as PD-L1–expressing tumor cells (TC) and immune cells (IC). The prognostic significance of these parameters on overall survival (OS) was evaluated, and their contribution to existing prognostic models was determined. High CD8+ TIL abundance (≥30% on stromal or intratumoral ICs) was seen in 61.3% patients and was associated with improved OS [HR, 0.4; 95% confidence interval (CI), 0.2–0.9; P = 0.017]. Although the expression of PD-L1 on TC was not prognostic, high expression of PD-L1 on ≥5% of intratumoral ICs was found in 38.5% patients and was significantly associated with improved OS (HR, 0.37; 95% CI, 0.15–0.93; P = 0. 023). Both high intratumoral IC PD-L1 expression and abundant CD8+ TILs in HPV+ OPSCCs identify subgroups of patients with excellent outcomes and provide additional prognostic information beyond existing staging systems. Cancer Immunol Res; 6(3); 295–304. ©2018 AACR.