Programmed death ligand 1 and CD8+ immune cell infiltrates in resected primary tracheal malignant neoplasms.

Abstract

Many patients with primary malignant tracheal neoplasms are not surgical candidates nor do they experience residual or recurrent disease after surgery and may benefit from alternative therapies. This study explores the expression of programmed death ligand 1 (PD-L1) in patients with primary tracheal malignancy as a biomarker for candidacy for treatment with immune checkpoint inhibitors. We conducted a retrospective review of the medical records of 23 patients with resected primary tracheal malignant tumours from 2010 to 2016. Paraffin-embedded blocks of tumour tissue were evaluated immunohistochemically to determine the expression of PD-L1 and infiltration by CD8+ immune cells. We identified 14 (61%) adenoid cystic carcinomas, 4 (17%) squamous cell carcinomas (SCC), 4 (17%) mucoepidermoid carcinomas and 1 adenosquamous carcinoma. PD-L1 expression was observed in 3 (75%) cases of SCC and 1 (100%) case of adenosquamous carcinoma, but it was absent in cases of adenoid cystic carcinomas and mucoepidermoid carcinomas. PD-L1 expression was significantly higher in tumours with a SCC component than in salivary-type tumours (P = 0.001). The presence of CD8+ immune cells in the tumour or peritumoural stroma was significantly higher in cases of tracheal tumours with a SCC component than in salivary-type tumours. Salivary-type primary malignant tracheal tumours do not significantly express PD-L1. In contrast, most primary tracheal tumours with a SCC component show membranous expression of PD-L1 and larger numbers of infiltrating CD8+ immune cells. PD-L1 expression may serve as a biomarker in patients with primary tracheal squamous cell malignant neoplasms when the patients are being considered for alternative treatments and inclusion in clinical trials. Protocol No. 2017P000415 (22 March 2017).