• Kazuki Takada, Tatsuro Okamoto, Fumihiro Shoji, Mototsugu Shimokawa, Takaki Akamine, Shinkichi Takamori, Masakazu Katsura, Yuzo Suzuki, Takatoshi Fujishita, Gouji Toyokawa, Yosuke Morodomi, Shinji Okano, Yoshinao Oda, and Yoshihiko Maehara.
• Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
• J Thorac Oncol. 2016 Nov 1; 11 (11): 1879-1890.

IntroductionThe clinicopathological features of carcinomas expressing programmed death ligand 1 (PD-L1) and their associations with common driver mutations, such as mutations in the EGFR gene, in lung adenocarcinoma are not clearly understood. Here, we examined PD-L1 protein expression in surgically resected primary lung adenocarcinoma and the association of PD-L1 protein expression with clinicopathological features, EGFR mutation status, and patient outcomes.MethodsThe expression of PD-L1 protein in 417 surgically resected primary lung adenocarcinomas was evaluated by immunohistochemical analysis. The cutoff value for defining PD-L1 positivity was determined according to the histogram of proportions of PD-L1-positive cancer cells.ResultsSamples from 85 patients (20.4%) and 144 patients (34.5%) were positive for PD-L1 protein expression according to 5% and 1% PD-L1 cutoff values, respectively. Fisher's exact tests showed that PD-L1 positivity was significantly associated with male sex, smoking, higher tumor grade, advanced T status, advanced N status, advanced stage, the presence of pleural and vessel invasions, micropapillary or solid predominant histological subtypes, and wild-type EGFR. Univariate and multivariate survival analyses revealed that patients with PD-L1 positivity had poorer prognoses than those without PD-L1 protein expression at the 1% cutoff value (disease-free survival p < 0.0001, overall survival p < 0.0001).ConclusionsPD-L1 protein expression was significantly higher in smoking-associated adenocarcinoma and in EGFR mutation-negative adenocarcinoma. PD-L1 protein expression was associated with poor survival in patients with lung adenocarcinoma. The PD-L1/programmed cell death 1 pathway may contribute to the progression of smoking-associated tumors in lung adenocarcinoma.Copyright © 2016 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

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