Association between clinicopathological features and prognosis significance of PD-L1 expression in small cell lung cancer patients: a systemic review and meta-analysis

BACKGROUND: Programmed death ligand-1 (PD-L1) has been identified as an established biomarker for predicting response to immunotherapy in a variety types of cancer. However, the clinicopathological and prognostic significance of this protein in small cell lung cancer (SCLC) patients remains controversial. METHODS: Eligible studies extracted from the databases of PubMed, MEDLINE, Embase, and CNKI databases were evaluated. Statistical analysis was performed using STATA 11.2 software. RESULTS: A total of 483 PD-L1+ cases and 570 controls from 11 publications were extracted. Either overall analysis or subcategory analysis showed that no significant association between higher PD-L1 expression and gender (n=8, OR 1.08, 95% CI: 0.73–1.61, P=0.704, I(2)=0.0%), tumor stage (n=5, OR 0.71, 95% CI: 0.20–2.56, P=0.599, I(2)=86.5%), smoking status (n=4, OR 0.85, 95% CI: 0.41–1.73, P=0.646, I(2)=0.0%), and the level of serum lactate dehydrogenase (LDH) (n=4, OR 0.76, 95% CI: 0.48–1.20, P=0.241, I(2)= 21.6%). PD-L1 expression had no positive correlation with overall survival (OS) (n=11, HR 0.97, 95% CI: 0.61–1.56, P=0.904, I(2)= 83.2%) in overall analysis. However, the stratified analysis showed that increased expression of PD-L1 predicted a significantly better OS in monoclonal antibody (mAb) subgroup and Food and Drug Administration (FDA) approved antibody clone specification (22C3/28–8/SP142/SP263) subgroup without significant heterogeneity. CONCLUSIONS: PD-L1 is not an important predictor of most clinicopathological features of SCLC patients, but it can predict an improved survival when using mAb or FDA approved clone specifications in IHC assays.