A comprehensive pan-cancer analysis of PD-L1 expression using clone E1L3N in Chinese patients with cancer.

Abstract

2656 Background: Immune checkpoint inhibitors (ICIs) benefit patients with multiple cancer types, and the expression of programmed death ligand 1 (PD-L1) protein assessed by immunohistochemistry (IHC) has been correlated with response and survival benefit from anti-PD-1/PD-L1 ICI therapies in several cancer types. IHC assay with E1L3N clone is currently approved by the NMPA for PD-L1 detection in non-small cell lung cancer (NSCLC), but its performance in other cancer types needs to be further validated. Thus, we performed this study to examine the prevalence of PD-L1 expression in a wide variety of tumor types in Chinese pan-cancer patients using the E1L3N antibody clone. Methods: From 2019 to 2022, a total of 13,647 patient across multiple tumor types were analyzed. Tumor tissue samples were subjected to IHC. PD-L1 expression was tested using the E1L3N PD-L1 IHC assay (Amoy Diagnostics, Xiamen, China), and scored with the tumor proportion score (TPS) and combined positive score (CPS). PD-L1 expression status was identified as positive and negative according to TPS or CPS. For NSCLC: negative (TPS < 1%), low expression (TPS 1-49%), and high expression (TPS ≥ 50%). For gastric/gastroesophageal junction carcinoma (GC/GJC): negative (CPS < 1), low expression (CPS 1-5), and high expression (CPS ≥ 5). For other cancer: negative (CPS < 1), low expression (CPS 1-10), and high expression (CPS ≥ 10). Results: In total, 14 cancer types were enrolled in the present study, including 68.2% NSCLC, 6.9% colorectal carcinoma (CRC), and 3.8% GC/GJC, and the remaining 21.1% include esophageal cancer (EC), breast cancer, cervical cancer (CC), biliary tract cancer (BTC), pancreatic cancer (PC), ovarian cancer, renal cancer, small cell lung cancer, urothelial carcinoma (UC), bladder cancer, head and neck squamous cell carcinoma (HNSCC), etc. PD-L1 positivity by TPS was observed in 52.5% NSCLC patients, similar to the frequency of PD-L1 expression in Chinese NSCLC patients detected using 22C3 clone. 76.0% and 36.7% of GC/GJC patients with PD-L1-positive tumors at a CPS cutoff of ≥ 1 and ≥ 5, respectively. PD-L1 positive expression frequency was higher than that in western GC/GJC patients detected using 22C3 and 28-8 clone (as reported from previous research: PD-L1 positivity with CPS ≥ 1 was 45.5% using the 22C3 assay and 49.1% using the 28-8 assay). 73.6% and 17.5% of CRC patients with PD-L1-positive tumors at a CPS cutoff of ≥ 1 and ≥ 10, respectively. In addition, 8 tumors (EC, CC, breast cancer, PC, BTC, UC, HNSCC, and bladder cancer) had the prevalence of PD-L1 CPS ≥ 1 greater than 50%. Conclusions: E1L3N can be used as a reliable alternative antibody clone to evaluate PD-L1 expression status not only in NSCLC patients but also in other cancer types.