Distribution of PD-L1 expression and its relationship with clinicopathological variables: an audit from 1071 cases of surgically resected non-small cell lung cancer.

Background: Programmed death ligand 1 (PD-L1) was reported to predict the response of immunotherapy; however, the association between PD-L1 expression and clinicopathologic characteristics has yet to be elucidated in non-small cell lung cancer (NSCLCs).

Materials And Methods: We reviewed PDL1 expression investigated by immunohistochemical analysis using FFPE tissue in a total of 1071 cases of primary or metastatic NSCLC tissues analyzed between 2015-2017, and evaluated the association between PD-L1 expression and the clinicopathologic characteristics.

Results: PD-L1 expression was observed in 361 (33.7%) cases with positive staining in at least 1% tumor cells and 116 (10.8%) cases had positive staining in ≥50% tumor cells. The PD-L1 positive prevalence was significantly higher in squamous cell carcinoma (SCC) than in adenocarcinoma (AD). In the AD subgroup, PD-L1 expression on tumors was higher in males and smokers, and with high histologic grade, relative high T, N, M status, advanced AJCC stage, and in ALK rearrangement patients. However, EGFR mutated patients showed relatively lower PD-L1 expression than wild type patients.

Conclusion: This study revealed the unique distribution of PD-L1 expression with clinicopathologic features in East Asian NSCLCs in a single, large cohort of patients. Since immunohistochemistry of the PD-L1 protein (PD-L1 IHC) is the only clinically approved predictive biomarker for anti-PD-1/-PD-L1 therapy currently, our outcomes could help to stratify patients to ensure selection of those who would most benefit from PD-1/PD- L1 inhibitor therapy.