Abstract
Programmed cell death-1 ligand 1 (PD-L1), tumor-infiltrating CD8-positive T lymphocytes (CD8-positive TILs), and cyclooxygenase-2 (Cox-2) have been used as prognostic tools in patients with lung adenocarcinoma. We conducted a retrospective review of data from 170 patients who had undergone pulmonary resection as an initial treatment for clinical T1-2 N0 lung adenocarcinoma. We then investigated the expressions of three biomarkers using immunohistochemical analyses and compared the expression levels with the clinicopathological characteristics and outcomes of the patients. Next, we classified the tumors into four groups based on the PD-L1 and CD8-positive TILs statuses and evaluated the prognostic significance of Cox-2 expression according to the tumor immune microenvironment classification. Tumors with positive PD-L1 expression levels had a significantly larger number of CD8-positive TILs than tumors with negative PD-L1 expression levels, whereas tumors with high Cox-2 expressions had significantly fewer CD8-positive TILs than tumors with low Cox-2 expressions. A multivariate analysis showed that histological subtype, nodal metastasis, CD8-positive TILs count, and PD-L1 expression were independent predictors of patient outcome. Using a classification based on the PD-L1 and CD8-positive TILs statuses, the outcomes of patients with a negative PD-L1 expression and a high CD8-positive TIL count were significantly better than those with other classifications. In patients with negative PD-L1 and low CD8-positive TILs, the rate of EGFR mutation was significantly higher than that in other classifications, and Cox-2 expression was a powerful predictor of outcome. Clinical and pathological features in conjunction with the tumor immune microenvironment classification indicate that lung adenocarcinoma should be divided into different subgroups for prognosis and treatment. Classification according to the PD-L1 and CD8-positive TILs statuses might enable the effects of Cox-2 inhibitor to be predicted.