Programmed Death-Ligand 1 Expression and EGFR Mutations in Multifocal Lung Cancer

Background Little is known about the programmed death-ligand 1 (PD-L1) expression in multifocal lung cancer, such as the expression in multiple primary lung cancer and pulmonary metastasis. In this translational study, we investigated PD-L1 expression and its relationship with the epidermal growth factor receptor (EGFR) mutation status in resected multifocal lung cancer. Methods The PD-L1 expression in 152 samples of multifocal lung cancer from 59 patients was evaluated by an immunohistochemical analysis. Results Among the 152 lung cancer lesions of 59 patients, PD-L1 expression was observed in 29 lesions (19.1%) of 20 patients (33.9%). Among 43 patients with 112 multiple primary lung cancer lesions, 15 lesions (13.4%) of 13 patients (30.2%) were PD-L1 positive; and among 16 patients with 40 pulmonary metastatic lesions, 14 lesions (35.0%) of 7 patients (43.8%) were PD-L1-positive. Among 43 patients with multiple primary lung cancer, there was disagreement of PD-L1 expression in 12 patients (27.9%, κ = 0.104). On the contrary, among 16 patients with pulmonary metastasis, disagreement of PD-L1 expression was observed only in 1 patient (6.3%, κ = 0.871). In pulmonary metastatic lesions, the frequency of PD-L1 positivity among lesions with wild-type EGFR was significantly higher than among lesions with mutated EGFR (66.7% versus 0%: p < 0.001). Conclusions This study provides important evidence of higher levels of agreement of PD-L1 expression in pulmonary metastasis compared with in multiple primary lung cancer, and high positivity of PD-L1 expression in pulmonary metastatic lesions with wild-type EGFR in an Asian population.