Clinicopathological and prognostic value of programmed death ligand-1 (PD-L1) in renal cell carcinoma: a meta-analysis

Background: Recently, the association of immunological checkpoint marker programmed death ligand-1 (PD-L1) and the prognosis of various cancers has always been a research hotspot. The objective of this study is to assess the clinical value of PD-L1 as a novel prognostic biomarker of renal cell carcinoma (RCC). Methods: Medline/PubMed, EMBASE, the Cochrane Library databases and Grey literature were searched up to 30 March 2015 for eligible studies of the association between PD-L1 expression and cancer-specific survival (CSS) in RCC. The risk ratio (RR) and its 95% confidence interval (CI) were calculated from the included studies. Moreover, the odds ratio (OR) was also extracted to evaluate the association between the clinicopathological parameters of participants and PD-L1 expression. Results: Five studies involving 1073 patients were included in the meta-analysis. The pooled results showed that positive/higher PD-L1 expression was a negative predictor for CSS with RR of 2.90 (95% CI: 1.64-5.13; P-heterogeneity. <= 0.001). Additionally, increased PD-L1 was found to be significantly associated with large tumor size (OR = 2.28, 95% CI: 1.61-3.23; P-heterogeneity. = 0.645), high TNM stage (OR = 4.37, 95% CI: 2.99-6.39; P-heterogeneity. = 0.676), poor nuclear grade (OR = 7.58, 95% CI: 5.26-10.92; P-heterogeneity. = 0.203) and present tumor necrosis (OR = 6.77, 95% CI: 4.73-9.71; P-heterogeneity. = 0.111) in renal cell carcinoma patients. Conclusion: The meta-analysis suggested that PD-L1 could act as a significant biomarker in the worse prognosis and adverse clinicopathologic features of renal cell carcinoma.