Clinical performance of endobronchial ultrasound‐guided transbronchial needle aspiration for assessing programmed death ligand‐1 expression in nonsmall cell lung cancer

Background Pembrolizumab was recently approved as a first line agent for metastatic NSCLC in patients with high programmed death‐ligand 1 (PD‐L1) expression. Objectives Since a significant portion of lung cancer is diagnosed by endobronchial ultrasound‐guided transbronchial needle aspiration (EBUS TBNA); there is a need for PD‐L1 testing in these specimens. However, to date few studies have evaluated performance of cytology specimens from EBUS TBNA for PD‐L1 analysis. Methods Patients who had a diagnosis of NSCLC and in whom ancillary testing, i.e., next generation sequencing (NGS), anaplastic lymphoma kinase (ALK), and PD‐L1 expression was requested between January and May 2017 were reviewed. Results Fifty of the 112 patients reviewed had the diagnosis of NSCLC for which ancillary testing was requested. Twelve patients (24%) had squamous cell carcinoma, twenty‐seven had adenocarcinoma (54%), five had NSCLC favor adenocarcinoma (10%), two had NSCLC favor squamous cell cancer (4%), and four had NSCLC not otherwise specified (NOS) (8%). Size of the lymph nodes or lesion sampled ranged from 10 to 50 mm. Four (8%) patients had insufficient number of tumor cells in the cell block for any of the ancillary molecular testing. Forty‐one (82%) patients had an adequate sample for all three ancillary tests. Satisfactory results for PD‐L1 expression for all cases was 86% with 14 (32%) patients having levels of PD‐L1 expression >50%. Conclusion EBUS TBNA is effective and has a high proportion of satisfactory results for testing PD‐L1 expression on tumor cells in addition to NGS and ALK FISH.