Prognostic and predictive values of PD-L1 expression in patients with digestive system cancer: a meta-analysis

BACKGROUND PD-L1 has been reported to be expressed in diverse human malignancies. However, the prognostic value of PD-L1 in digestive system cancers remains inconclusive. Therefore, we conducted this meta-analysis to evaluate the prognostic impact of PD-L1 expression in digestive system cancers. MATERIALS AND METHODS We searched the PubMed, Embase, and the Chinese National Knowledge Infrastructure for publications concerning PD-L1 expression in digestive system cancers. Correlations of PD-L1 expression level with overall survival (OS), disease-free survival (DFS), and recurrence-free survival (RFS) were analyzed. RESULTS Finally, 32 studies with 7,308 patients were included. Our results show that PD-L1 expression was significantly associated with poorer OS (hazard ratio [HR] =1.44, 95% confidence interval [CI] =1.18-1.76, P<0.001), but not DFS (HR =0.91, 95% CI =0.61-1.37, P=0.657) or RFS (HR =1.27, 95% CI =0.75-2.14, P=0.368). Moreover, in the subgroup analysis, significant associations between PD-L1 expression and OS were found in Asians (HR =1.50, 95% CI =1.19-1.89, P=0.001), gastric cancer (HR =1.43, 95% CI =1.05-1.94, P=0.021), and pancreatic carcinoma (HR =2.64, 95% CI =1.78-3.93, P<0.001). CONCLUSION These results suggest that the expression of PD-L1 is associated with worse OS in digestive system cancers, especially in gastric cancer and pancreatic cancer. In addition, PD-L1 may act as a new parameter for predicting poor prognosis and a promising target for anticancer therapy in digestive system cancers.