Correlation of programmed death ligand 1 expression with overall survival, clinical, and pathological features in patients with malignant plural mesothelioma

Abstract

Background and aim Recent studies have proposed high expression of programmed death ligand 1 (PD-L1) in pleural tumors. Thus, we conducted the present study to examine the expression of PD-L1 in malignant pleural mesothelioma (MPM), to analyze the association between PD-L1 expression and clinicopathological features, and to correlate PD-L1 expression with overall survival (OS).Materials and methods A retrospective study on 54 cases of pleural mesothelioma was conducted. Using an automated stainer (BenchMark Ventana), the sections were stained with the following antibodies according to the standard protocol and the manufacturer’s recommendations for each antibody: PD-L1 and Ki-67. Tumors were deemed positive for PD-L1 if membranous and/or cytoplasmic staining was present in more than 1% of tumor cells.Results The median age was 65 years (range, 45–87 years), and 81.5% of the patients were men. PD-L1 was expressed on the cell membrane and cytoplasm of tumor cells in 23 (42.6%) cases. PD-L1 expression was significantly associated with the histopathological type (P<0.001). In addition, positive PD-L1 expression in tumor cell was associated with advanced stage (P<0.001) and high Ki-67 (P=0.031). Kaplan–Meier analysis demonstrated that PD-L1 expression in tumor cells was significantly associated with OS. Cases with positive PD-L1 expression had a shorter OS (median, 12 vs. 30 months with negative PD-L1 expression) (P=0.001). In univariate Cox regression analysis, high PD-L1 expression was confirmed to be associated with OS (hazard ratio, 0.24; 95% confidence interval, 0.1–0.57; P=0.001). Patients with epithelioid histology had a significantly longer OS than the other histopathological subtypes (P<0.001).Conclusion In conclusion, PD-L1 expression is associated with poor OS in MPM. Further, this study confirms the better prognostic profile of epithelioid MPM, compared with other histologic subtypes.