Programmed death-ligand-1 expression in non-small cell lung cancer and prognosis

Abstract

Background: Prognostic significance of the programmed death-ligand-1 status in non-small cell lung carcinoma remains controversial. Aims: To show the programmed death-ligand-1 expression status in patients with non-small cell lung carcinoma and its effect on the prognosis and the relationship with clinicopathologic data. Study Design: Retrospective cross-sectional study. Methods: The study included 208 cases who were diagnosed with NSCLC and who underwent surgical resection between 2001 and 2012. Programmed death-ligand-1 (SP142 clone) was applied to the histological sections acquired from the microarray paraffin blocks with immunohistochemistry. Staining intensity was scored as weak (+, 1), moderate (++, 2), and strong (+++, 3). Percentage (0%-100%) was multiplied by staining intensity (1-2-3) to calculate the H score. Four different cut-off values were used; 1: ≥1% (independent of intensity), 2: ≥5% (independent of intensity), 3: ≥5% moderate/strong staining (except for weak staining), 4: H score ≥30 values were considered positive. In this study, staining a single cell at any intensity was considered positive. Results: Thirty-four out 208 cases (16.3%) had PDL-1 positive staining. PDL-1 expression was observed in patients with non-small cell lung carcinoma independent of the histological type or subtype (range; 0-25%). When the cut-off level was set to ≥5% with moderate and strong staining, the median overall survival was 45 months for the PD-L1 positive group and not reached for the PD-L1 negative group (p-value 0.024). PD-L1 positivity was significantly higher in patients over the age of 60 years and in cases with a tumor diameter of more than 5 cm (p=0.023 and 0.025, respectively). Conclusion: PD-L1 expression is positive in 16.3% of patients with non-small cell lung cancer and may have a negative prognostic value.