Abstract 5463: The PD-L1 protein expression in Chinese patients with recurrent or metastatic head and neck squamous cell carcinoma: A multi-center retrospective study

Abstract Programmed death-ligand 1 (PD-L1) is a trans-membrane protein and co-inhibitory factor of the immune response. PD-L1 can combine with its receptor (PD-1) to reduce the proliferation of PD-1-positive cells and induce apoptosis. Therefore, PD-L1 was employed as a prognostic marker and a target for anti-cancer immunotherapy in blocking the PD-1 and PD-L1 checkpoints. PD-L1 is highly expressed in various malignancies, including head and neck squamous cell carcinoma (HNSCC). HNSCC is the sixth most common cancer worldwide, with high incidence and mortality rates in China. Although PD-L1 expression has been widely investigated, the PD-L1 expression status in Chinese HNSCC patients (pts) is largely unrevealed. The primary objective of this study was to determine the prevalence of PD-L1 expression with the Combined Positive Score (CPS) ≥20 in Chinese pts with recurrent or metastatic (R/M) HNSCC. The secondary objectives were to determine the prevalence of CPS≥1 in pts with R/M HNSCC and to study the difference in the demographic characteristics, clinicopathological parameters, treatment status, and other available biomarkers between the PD-L1 CPS≥20 group and the PD-L1 CPS<20 group. This study was a multi-center retrospective analysis of data from six centers in China from August 9, 2021, to February 28, 2022. Pts with histologically/cytologically confirmed diagnoses of R/M HNSCC were included. PD-L1 expression was assessed by IHC using the 22C3 PharmDx assay (Agilent, Santa Clara, CA, USA) and was determined using a CPS. The Chi-square test, Fisher’s exact test, or Wilcoxon rank sum test would be used to compare the prevalence of these variables among pts between the PD-L1 CPS≥20 group and the PD-L1 CPS<20 group. Out of 406 enrolled pts with R/M HNSCC, 402 testing pts were included in the final analysis. For all testing R/M HNSCC pts, 168 pts (41.8% [95% CI 36.92-46.78]) had PD-L1 expression with CPS ≥20. In addition, 337 pts (83.8% [95% CI 79.86-87.29]) had PD-L1 expression (CPS≥1). For the testing pts, there were statistically significant differences in variables of gender (P < 0.001), smoking habit (P = 0.0138 for non-smokers versus current smokers), and primary tumor site (P < 0.001 for hypopharynx versus oral cavity and P = 0.0304 for larynx versus oral cavity) between the PD-L1 CPS≥20 group and the PD-L1 CPS<20 group. In summary, in Chinese R/M HNSCC pts, most pts (83.8%) had PD-L1 expression, and two-fifths (41.8%) had PD-L1 expression with CPS ≥20. Prevalence of PD-L1 among Chinese pts with R/M HNSCC was consistent with that reported in the global KEYNOTE-048 study. PD-L1 expression was significantly associated with gender, smoking history and primary tumor site. Our findings of the variables related to the PD-L1 expression levels can supply adjuvant evidence for clinical practice and are a solid basis for future research on immunotherapy. Citation Format: Haizhen Lu, Dong Kuang, Lili Jiang, Jingping Yun, Qingxin Xia, Jian Wang, Pei Duan, Ping Zhou, Shengbing Zang, Yiping Jin, Xiangnan Jiang, Jielin Li, Wenmin Tang, Jiansong Zhou, Jihua Chen, Jianming Ying. The PD-L1 protein expression in Chinese patients with recurrent or metastatic head and neck squamous cell carcinoma: A multi-center retrospective study. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5463.