The prognostic value of programmed cell death ligand 1expression in non-Hodgkin lymphoma:a meta-analysis

Objective: Although the prognostic value of programmed cell death-ligand 1(PD-L1) expression in non-Hodgkin lymphoma(NHL) has been evaluated in many studies, the results remain controversial. To investigate the prognostic role of PD-L1 expression and the association between PD-L1 expression and clinicopathological features of NHL, we performed a meta-analysis.Methods: The Pub Med, EMBASE, and Cochrane Library databases were searched up to November 30, 2017. The hazard ratio(HR), 95% confidence interval(CI), and odds ratios(OR) with 95% CIs were combined to evaluate the association of PD-L1 expression with overall survival(OS) and clinicopathological features. Review manager 5.3 and STATA 12.0 were used in this meta-analysis.Results: A total of 2,005 patients across nine studies were enrolled in our meta-analysis, and the pooled results showed that high PD-L1 expression was associated with a poor prognosis(HR=2.04, 95% CI: 1.18–3.54, P=0.01). In the subgroup analysis according to histology types, pooled results demonstrated that an increased PD-L1 expression was an unfavorable prognostic factor for diffuse large B-cell lymphoma(HR=1.92, 95% CI: 1.06–3.48, P=0.03) but not for natural killer/T-cell lymphoma(HR=2.41, 95%CI: 0.47–12.22, P=0.29). Pooled ORs indicated that PD-L1 expression was higher in NHL with international prognostic indices of≥3. However, PD-L1 expression had no correlation with gender, age, disease stage, lactate dehydrogenase level, B symptoms, and germinal center B-cell-like lymphoma.Conclusions: High PD-L1 expression was a poor prognostic biomarker in patients with NHL. Because of our limited sample size,high-quality studies with larger sample sizes are needed to validate our results.