Prognostic factors of resected pathological stage I lung adenocarcinoma: evaluating subtypes and PD-L1/CD155 expression.

We aimed to compare the prognostic impacts of adenocarcinoma subtypes, programmed death-ligand I (PD-L1), and CD155 expression on patients with resected pathological stage (p-stage) I lung adenocarcinoma. In total, 353 patients with completely resected p-stage I lung adenocarcinomas were retrospectively reviewed. The expression levels of PD-L1 and CD155 in tumour cells from each adenocarcinoma subtype were evaluated using several clinicopathological and histological features, such as the presence of a micropapillary pattern. A total of 52 patients (14.7%) had PD-L1-positive tumours, whereas 128 patients (36.3%) had CD155-positive tumours, with a tumour proportion score of 5% for both PD-L1 and CD155 expression. Compared with patients with other adenocarcinoma subtypes, those with solid-predominant adenocarcinomas were significantly more positive for PD-L1 and CD155. Multivariate analysis showed that PD-L1 expression status was significantly associated with progression-free survival and overall survival, whereas CD155 expression and the presence of a micropapillary pattern were not significantly associated with either parameter. Patients with PD-L1-positive tumours had poorer prognoses than those with CD155-positive tumours. Moreover, PD-L1 and CD155 were significantly expressed in solid-predominant adenocarcinomas. The results of this study suggest that immune checkpoint inhibitors can be used as adjuvants in the treatment of patients with p-stage I adenocarcinoma.