Prognostic significance of PD-L1 expression in patients with colorectal cancer: a meta-analysis*

Abstract

Abstract Background The association between the expression of programmed cell death 1 (PD-1) or its ligand [programmed cell death ligand-1 (PD-L1)] and colorectal cancer (CRC) survival rates remains unclear. Thus, we conducted a meta-analysis to investigate the prognostic value of PD-L1 expression in CRC patients. Methods All eligible studies related to evaluation of PD-L1 expression and survival of CRC patients were searched in PubMed, Medline, Cochrane library, and the EMBASE database. Hazard ratios (HRs) and 95% confidence intervals (CI) of overall survival (OS) were examined to assess the effect of PD-L1 expression on the survival of CRC patients. The outcomes of this meta-analysis were synthesized based on random-effects model. Subgroup analyses were also performed. Results Seven studies, wherein OS data were stratified according to the expression status of PD-L1, were analyzed. CRC patients showing positive PD-L1 expression were associated with significantly poorer prognoses in terms of overall survival, compared with those displaying negative PD-L1 expression (HR = 1.43, 95% CI: 1.07-1.92; P = 0.02). In the subgroup analyses, H-scores as well as the percentage of stained cells indicated that PD-L1 expression was significantly associated with poor prognosis (HR = 1.90, 95% CI: 1.38-2.62, P < 0.01; HR = 1.81, 95% CI: 1.08-3.03, P = 0.02). Immunohistochemical staining, utilizing a rabbit anti-PD-L1 antibody, revealed significantly superior survival in the PD-L1 negative group compared with the PD-L1 positive expression group (HR = 1.92; 95% CI, 1.40-2.63; P < 0.01). Moreover, PD-L1 expression was significantly associated with poor prognosis when polyclonal antibodies were used (HR = 1.84; 95% CI, 1.30-2.61; P < 0.01). Conclusion Our meta-analysis indicated that PD-L1 expression status is a significant prognostic factor for CRC patients. Positive PD-L1 expression was associated with worse CRC survival. Evaluation via different immunohistochemistry based techniques may partly account for the contradictory results. Therefore, further investigative studies using larger sample sizes are felt to be needed to elucidate the prognostic value of PD-L1 expression in CRC patients.