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

OBJECTIVE: To analyze the prognostic value of programmed death factor ligand 1 (PD-L1) in colorectal cancer. METHODS: Electronic 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. RESULTS: A 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. CONCLUSION: The 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. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12957-018-1544-x) contains supplementary material, which is available to authorized users.