Expression Levels Of PD-L1 And EGFR In Gastric Cancer And Their Impacts On Patient Prognosis

Objectives: We aimed to evaluate the expression levels of programmed death ligand 1(PD-L1)and epidermal growth factor receptor(EGFR)in gastric cancer,to explore the impacts of both proteins on clinicopathologic characteristics as well as patient prognosis.Methods: Two slides of gastric cancer tissue microarray consisting of 90 cases were purchased.Immunohistochemistry was applied to detect PD-L1 and EGFR in gastric cancer tissue as well as adjacent normal tissue.Rank sum test was adopted to determine whether there existed a significant expression difference between cancer tissue and normal tissue.Chi-square test was adopted to explore the impacts of different proteins levels on patient clinicopathologic characteristics.Kaplan-Meier analysis and log-rank test were adopted to evaluate the impacts of PD-L1 and EGFR on patient overall survival(OS).Univariate and multivariate models were applied to identify potential prognostic factors.Results: Positivity of PD-L1(29.07%)and EGFR(35.71%)are both significantly higher in gastric cancer tissue than normal tissue(P=0.036,P<0.001).PD-L1 positivity varies significantly(Fisher's exact test,P=0.006)among tumors located in gastric cardia(63.63%),gastric atrum(30.61%),and gastric body(11.54%).Patients aging 70 or over showed higher EGFR positivity(?2=7.827,P=0.005).Kaplan-Meier analysis demonstrated that patients with elevated expression of PD-L1 and EGFR presented significantly shorter overall survival(log-rank ?2=4.074,P=0.044;log-rank ?2=7.668,P=0.006).Univariate analysis revealed that PD-L1 positive expression(HR=1.793,P=0.049),EGFR positive expression(HR=2.178,P=0.008),low differentiation(HR=2.019,P=0.016),vascular invasion(HR=3.224,P<0.001),depth of invasion(HR=2.028,P=0.038),lymph node invasion(HR=2.653,P=0.001)and distant metastasis(HR=2.799,P=0.006)were associated with worse overall survival.Larger tumor size(?5cm)tended to indicate worse OS(HR=1.688,P=0.063).Multivariate analysis identified PD-L1 expression(HR=2.351,P=0.023),low differentiation(HR=2.090,P=0.047),vascular invasion(HR=2.312,P=0.043),Lymph node invasion(HR=2.253,P=0.045)and distant metastasis(HR=2.792,P=0.023)to be potential independent prognostic factors for OS.No correlation was found between PD-L1 and EGFR expression,yet patients with co-expression of both PD-L1 and EGFR tended to show a worse prognosis than the rest(log-rank ?2=3.468,P=0.063).Conclusions: Our findings suggest that elevated expression levels of PD-L1 and EGFR are prognostic factors for shorter overall survival,respectively.