Programmed cell death-ligand 1 (PD-L1) expression is associated with RAS/TP53 mutations in lung adenocarcinoma.

INTRODUCTION: The systematic assessment of anti-programmed cell death ligand 1 (PD-L1) expression by immunohistochemistry (IHC) in lung adenocarcinomas is becoming standard practice. However, the assessment of PD-L1 expression on small tissue specimens needs to be evaluated and the association with other features more thoroughly analyzed.

METHODS: This retrospective single center study evaluated the immunohistochemical expression of the SP263 anti-PD-L1 antibody on tissue microarrays (TMA) of 152 surgically resected lung adenocarcinomas, using a 25% positivity threshold. The positive cases and 50 randomly chosen negative cases in tissue microarray (TMA) were reassessed on whole tissue sections. The results were correlated to clinical, histopathological and to molecular data obtained through the screening of 214 mutations in 26 genes (LungCarta panel, Agena Biosciences).

RESULTS: Among 152 primary lung adenocarcinomas, 19 cases (13%) showed PD-L1 expression. The agreement between TMA and whole tissue sections was 89%, specificity was 97%. PD-L1 expression was correlated to RAS mutations (p = .04), RAS/TP53 co-mutations (p = .01) and to the solid or acinar subtype (p = .048).

CONCLUSIONS: With the SP263 PD-L1 antibody, small samples appear as a reliable means to evaluate the PD-L1 status in lung adenocarcinoma. The association between PD-L1 expression and RAS/TP53 mutations may have clinical relevance to predict the efficacy of PD-1/PD-L1 immune checkpoints inhibitors.