Abstract 6658: Prevalence of PD-L1 expression and its correlation with tumor biomarkers in the Chinese muscle invasive urothelial bladder carcinoma patients
Authors: Fan Yu , Dai Tao , Zhang Dahong , Guo Hongqian , Zhou Fangjian , Shi Benkang , Wang Shaogang , Ji Zhigang , Wang Chunxi , Yao Xudong , Wei Qiang , Chen Nanhui , Xing Jinchun , Yang Jinjian , Kong Chuize , Huang Jian , Ye Dingwei , Zhou Liqun 
Published: April 2023

Abstract
The association of programmed cell death-ligand 1 (PD-L1) expression with the activity of immune checkpoint inhibitor therapy setting has encouraged us to study the prevalence of PD-L1 in muscle invasive urothelial bladder cancer (MIUBC) patients. Since, the prevalence of PD-L1 expression and its prognostic role in MIUBC is unclear in China, we conducted a multi-center, prospective, epidemiological study to investigate prevalence of high PD-L1 expression and its correlation with other exploratory biomarkers including CD8+ T cells and tumor mutation burden (TMB) in Chinese MIUBC patients (NCT03433924). The study enrolled newly diagnosed, untreated MIUBC patients from 17 hospitals in China. High PD-L1 expression by Ventana PD-L1 [SP263] assay was defined as 1) ≥25% tumor cell (TC) + or 2) tumor associated immune cell (IC) area &gt;1%: ≥25% IC+; 3) IC area=1%: 100% IC+. The primary outcome was prevalence of high PD-L1 expression; secondary outcome was PD-L1 expression profile in TC or IC in patients. An exploratory study was conducted to investigate the percentage of patients with high infiltration of CD8+ T cells and elevated TMB using immunohistochemistry and next generation sequencing, respectively. High CD8+ and TMB status was considered if it refers to ˃ median value (3%) and ˃10 mut/Mb, respectively. Association of PD-L1 expression with demographic and baseline characteristics was evaluated by logistic regression model while PD-L1 with tumor biomarkers were evaluated by spearman’s rank correlation coefficient. Overall, 248 MIUBC patients were enrolled and 229 patients with PD-L1 data were included. High PD-L1 expression was observed in 52.4% patients. High PD-L1 expression was positive in 59 (25.8%) patients of TC and 82 (35.8%) patients of IC. CD8+ T cell and TMB showed high expression in 44.5% and 54.1% patients, respectively, with mean TMB of 14.14 mut/Mb. The exploratory analysis showed no significant association of PD-L1 expression with age, gender, primary tumor site, metastatic disease, regional lymph node, tobacco use or AJCC stage. Further a weak and positive correlation was observed between percentage of TC with membrane PD-L1 positivity and CD8+ T cells (0.34, 95%Cl, 0.22 - 0.45, p˂0.001), IC with membrane PD-L1 positivity and CD8+ T cells (0.44, 95%Cl, 0.33 - 0.54, p˂0.001), TC with membrane PD-L1 positivity and TMB (0.05, 95%Cl, -0.08 - 0.19, p=0.441), IC with membrane PD-L1 positivity and TMB (0.16, 95%Cl, 0.02 - 0.29, p=0.020). In conclusion, our study showed high prevalence of PD-L1 expression in patients with MIUBC along with their weak, positive correlation with CD8+ T cells and TMB. These findings are consistent with other studies that show that PD-L1 and TMB stand as the most robust predictive biomarkers, but may be uncorrelated. With subsequent follow-up time, the effect of biomarkers on survival will be assessed in future study.
Citation Format: Yu Fan, Tao Dai, Dahong Zhang, Hongqian Guo, Fangjian Zhou, Benkang Shi, Shaogang Wang, Zhigang Ji, Chunxi Wang, Xudong Yao, Qiang Wei, Nanhui Chen, Jinchun Xing, Jinjian Yang, Chuize Kong, Jian Huang, Dingwei Ye, Liqun Zhou. Prevalence of PD-L1 expression and its correlation with tumor biomarkers in the Chinese muscle invasive urothelial bladder carcinoma patients [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 6658.