Correlation between PD-L1 expression and clinicopathological characteristics of non-small cell lung cancer: A real-world study of a large Chinese cohort.

Background: Programmed death ligand-1 (PD-L1) is a predictive marker of anti-programmed death protein 1 (PD-1)/PD-L1 therapies for non-small cell lung cancer (NSCLC). However, little is known between PD-L1 expression and the clinicopathological characteristics of NSCLC in the Chinese population in a real-world setting.

Methods: We analyzed PD-L1 expression by immunohistochemistry (IHC) in NSCLC patients using the 22C3 clone on the Dako Autostainer Link 48 platform. We then examined the associations of PD-L1 expression with clinicopathological characteristics, stromal tumor-infiltrating lymphocytes (TILs) and major molecular features.

Results: A total of 1,156 recently NSCLC specimens including 827 sequentially resected specimens and 293 biopsy specimens were enrolled in our study. PD-L1 high expression was observed in 9.7% of 827 NSCLC patients, including 6.5% with adenocarcinoma (ADC, n=690), and 27.4% with squamous cell carcinoma (SqCC, n=117). These results showed higher expression rates than those in archived samples (>5 years old, n=329), that were previously reported by our group (4.9%, 0.5%, and 13.9% in NSCLC, ADC, and SqCC, respectively). The prevalence of PD-L1 expression was lower in surgical resection samples than in small biopsy samples. PD-L1 high expression in the lung biopsy was less likely present in the primary cancer than in metastases, and was also associated with a high level of stromal TILs (P=0.029) and PD-L1-positive immune cells (IC) (P<0.001). Both PD-L1 high and low expressions were more frequent in EGFR-wild type than in mutant type (P<0.001).

Conclusions: This study demonstrates that expression of PD-L1 is linked to the type of tumor specimens, resection versus biopsy specimens, and biopsies of primary versus metastatic cancers. These findings have substantial implications for clinical practice.