Author：Yanhui Chen, Yating Wang, Bohang Yang, Ying hu, Hui Zeng, Henghui Zhang

Background: Recent studies have proposed programmed cell death 1 ligand (PD-L1) expression as a distinct biomarker of response to anti-PD-1/PD-L1 therapies. The PD-L1 positive rates in newly diagnosed advanced common solid tumours in China were evaluated. 

Methods: 742 cases of advanced respiratory and digestive system tumour patients were included, including nasopharyngeal carcinoma (33), lung adenocarcinoma (243), lung squamous cell carcinoma (110), small cell lung cancer (20), esophageal cancer (34), gastric cancer (42), duodenal carcinoma (10), colon cancer (78), rectal cancer (31), hepatocellular carcinoma (31), cholangiocarcinoma (67), gallbladder cancer (10), and pancreatic cancer (33). Tumour tissue samples were collected to detect PD-L1 expression by immunohistochemistry (using the SP142 antibody). 

Results: According to PD-L1 strong positive ratio (≥50% in tumour cells (TC), or ≥10 % in immune cells (IC)), in respiratory system tumours, nasopharyngeal carcinoma had the highest strong positive rates of PD-L1, 42% in TC and 21% in IC, followed by lung squamous cell carcinoma (26% in TC and 17% in IC) and lung adenocarcinoma (21% in TC and 12% in IC). Small cell lung cancer did not have PD-L1 strong positive cases. In digestive system tumours, the positive rates of PD-L1 in TC were higher in gallbladder, esophageal and pancreatic cancer, which were 10%, 6% and 6% respectively, followed by colon cancer (3%), gastric cancer (2%) and cholangiocarcinoma (1%). Duodenal carcinoma, rectal cancer and hepatocellular carcinoma did not have PD-L1 strong positive cases in TC. The positive rates of PD-L1 in IC were higher in rectal cancer, hepatocellular carcinoma, gallbladder cancer and cholangiocarcinoma, which were 23%, 23%, 20% and 18% respectively, followed by esophageal cancer (9%), gastric cancer (10%) and colon cancer (10%). Duodenal carcinoma and pancreatic cancer did not have PD-L1 strong positive cases in IC. 

Conclusions: The PD-L1 strong positive rates of respiratory system tumours were higher than the digestive system tumours. The role of PD-L1 as a predictor of efficacy of PD-1/PD-L1 inhibitors in different types of cancers needs further evaluation.