Prognostic and clinicopathological significance of PD-L1 in patients with renal cell carcinoma: a meta-analysis based on 1863 individuals.

The prognostic significance of PD-L1 in renal cell carcinoma (RCC) had been investigated in previous studies; however, the results remain controversial. The primary aim of this meta-analysis was to investigate the prognostic and clinicopathological significance of the PD-L1 expression in patients with RCC. Relevant literature was identified form PubMed, Embase, Web of Science and Cochrane library, which compared the prognostic significance between PD-L1 expression and RCC. Hazard ratios (HRs) for survival outcomes and odds ratios (ORs) for clinical parameters associated with PD-L1 were extracted from eligible studies. Heterogeneity was assessed using the I2 value. The fixed-effects model was used if there was no evidence of heterogeneity; otherwise, the random-effects model was used. Publication bias was evaluated using Begg's funnel plots and Egger's regression test. A total of 1863 patients from ten eligible studies were analyzed. The results showed that PD-L1 expression is associated with poor overall survival in clear cell RCC (ccRCC) (HR = 2.76, 95%CI: 2.25-3.38, I2 = 14.4%, P < 0.001) and non-clear cell RCC (non-ccRCC) (HR = 2.77, 95%CI: 1.62-4.72, I2 = 28.8%, P < 0.001). In addition, PD-L1 expression was found to be significantly associated with primary tumor stage (OR = 1.76, 95%CI: 1.39-2.23; I2 = 56.3%), regional lymph node involvement (OR = 2.10, 95%CI: 1.48-2.98; I2 = 14.9%), distant metastases (OR = 2.69, 95%CI: 2.05-3.54; I2 = 0.0%), nuclear grade (OR = 1.72, 95%CI: 1.32-2.23; I2 = 79.4%) and histologic tumor necrosis (OR = 2.25, 95%CI: 1.59-3.18; I2 = 66.1%) in patients with RCC. The outcome stability was confirmed by sensitivity analysis. Both the Begg's funnel plot test (P = 0.276) and the Egger's (P = 0.388) verified that there was no publication bias within the included studies. This study suggests that PD-L1 expression is correlated with poor prognosis and advanced clinicopathological features in RCC patients.