Relevance Between Programmed Death Ligand 1 and Radiologic Invasiveness in Pathologic Stage I Lung Adenocarcinoma

Background. Programmed death ligand 1 (PD-L1) was reported to predict the response of immunotherapy; however, the association between PD-L1 expression and radiologic and pathologic features has yet to be elucidated. Methods. In all, 292 patients with resected pathologic stage I adenocarcinoma were analyzed for PD-L1 expression by immunohistochemistry and evaluated to determine the association between PD-L1 expression and the radiologic/pathologic invasiveness. Specifically, the radiologic invasiveness and noninvasiveness were determined based on the consolidation/tumor ratio, with a cutoff value of 0.25 by thin-section computed tomography. Results. Among 292 patients, 47 (16.1%) were positive for PD-L1 expression; the remaining 245 patients (83.9%) were negative for PD-L1 expression. Fisher's exact test demonstrated that PD-L1 expression was significantly associated with a higher consolidation/tumor ratio (p = 0.029) and higher maximum standardized uptake value (p = 0.004). The mean values of consolidation/tumor ratio and maximum standardized uptake in patients with and without PD-L1 expression were 0.845 +/- 0.052 and 7.241 +/- 0.795, and 0.607 +/- 0.023 and 3.60 +/- 0.364, respectively (p < 0.001 and p < 0.001, respectively). Among 47 adenocarcinomas harboring PD-L1 expression, the frequencies of PD-L1 expression for consolidation/ tumor ratios of 0, 0.1 to 0.25, 0.26 to 0.5, and 0.51 or more were 6.4%, 2.1%, 4.3%, and 87.2%, respectively (p = 0.007). Pathologically, PD-L1 was identified exclusively only in more invasive subtypes, not in less invasive ones, such as atypical adenomatous hyperplasia, adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic predominant ones (p < 0.001). Conclusions. Expression of PD-L1 was significantly associated with radiologic/pathologic invasive adenocarcinomas. This study provides the first evidence of the radiologic and pathologic invasiveness in resected pathologic stage I adenocarcinoma with PD-L1 expression. (C) 2017 by The Society of Thoracic Surgeons