PD-L1 Expression in Patients with Non-small Cell Lung Cancer

Aim: The aim of this study was to evaluate whether irradiation induces the expression of tumor programed cell death ligand 1 (PD-L1) in patients with non-small cell lung cancer (NSCLC). Patients and Methods: Seventeen patients with NSCLC who received chemoradiotherapy and underwent tumor resection and six patients whose pre-treatment biopsy specimens were available, were analyzed by immuno histochemistry for PD-L1 expression between September 2011 and June 2016 at the Institute of Biomedical Research and Innovation Hospital. Results: Among six patients for which pre-irradiation biopsy samples were available, the H-score for PD-L1 was reduced after irradiation following staining with two different antibody clones (SP28-8 and SP142). A PD-L1 H-score > 5 with SP28-8 antibody (hazard ratio= 6.46; 95% confidence interval= 1.209-34.53; p= 0.029) was a significant negative factor for duration of progression-free survival after curative operation or chemoradiation. Conclusion: We showed that tumor PD-L1 expression decreased in patients with NSCLC who received chemoradiotherapy and radiation resistance might be due to pre-treatment PD-L1 expression.