Relationship of tumor PD-L1 expression with EGFR wild-type status and poor prognosis in lung adenocarcinoma

Programmed death-ligand 1 is an immune modulator that promotes immunosuppression by binding to programmed death-1 of T-lymphocytes. Whereas programmed death-ligand 1 expression has been shown to be associated with the clinical response to anti-programmed death-ligand 1 antibody, the association of tumor programmed death-ligand 1 expression with clinicopathological/molecular features and with prognosis remains inconclusive in lung adenocarcinoma. We therefore examined the association of programmed death-ligand 1 expression with the clinicopathological/molecular features and prognosis of lung adenocarcinoma.

Using tissue microarrays of 268 consecutive cases of lung adenocarcinoma, we evaluated programmed death-ligand 1 expression by immunohistochemistry. We examined the association of programmed death-ligand 1 expression with clinicopathological and molecular features. We also examined the prognostic association of programmed death-ligand 1 expression, using the log-rank test as well as Cox proportional hazards regression models to compute the mortality hazard ratio (HR).

Programmed death-ligand 1 immunoreactivity (at least 5% of the tumor cells) was observed in 43 (16%) of 268 cases of lung adenocarcinoma. Programmed death-ligand 1 positivity was associated with less tumor differentiation (P < 0.0001) and EGFR wild-type status (P = 0.0008). In a multivariable logistic regression analysis, less tumor differentiation was independently associated with programmed death-ligand 1 positivity (multivariable odds ratio, 6.54; 95% confidence interval [CI], 2.37-23.3; P = 0.0001). Programmed death-ligand 1 positivity was associated with a poor prognosis for lung cancer-specific survival (log-rank, P = 0.019; HR, 1.73; 95% CI, 1.06-2.72; P = 0.030) and overall survival (log-rank, P = 0.0014; HR, 1.88; 95% CI, 1.25-2.74).

Our study demonstrated that programmed death-ligand 1 positivity in lung adenocarcinoma was associated with less tumor differentiation and EGFR wild-type status, as well as a poor prognosis.