Clinicopathological and prognostic significance of PD-L1 expression in colorectal cancer: a systematic review and meta-analysis

ObjectiveTo analyze the prognostic value of programmed death factor ligand 1 (PD-L1) in colorectal cancer.MethodsElectronic databases, such as PubMed, Web of Science, Embase, and Cochrane library, were searched to identify studies evaluating the PD-L1 expression and overall survival (OS) in these patients. Afterwards, the relevant data were extracted to perform the meta-analysis.ResultsA total of 3481 patients were included in 10 studies. The combined hazard ratio (HR) was 1.22 (95%CI=1.01-1.48, P=0.04), indicating that high expression of PD-L1 was significantly correlated with poor prognosis of colorectal cancer. Apropos of clinicopathological features, the merged odds ratio (OR) exhibited that highly expressed PD-L1 was firmly related to lymphatic invasion (OR=3.49, 95%CI=1.54-7.90, P=0.003) and advanced stage (OR=1.77, 95%CI=1.41-2.23, P<0.00001), but not correlative with patients' gender, microsatellite instability, or tumor location.ConclusionThe expression of PD-L1 can be utilized as an independent factor in judging the prognosis of colorectal cancer, and patients with advanced cancer or lymphatic invasion are more likely to express PD-L1. This conclusion may lay a theoretical foundation for the application of PD-1/PD-L1 immunoassay point inhibitors but still needs verifying by sizeable well-designed cohort studies.