PD-L1 testing on the EBUS-FNA cytology specimens of non-small cell lung cancer

The FDA approved PD-L1 tests for anti-PD-L1 immunotherapy are for surgical or histology specimens. It is not clear if cytology specimens could be used for PD-L1 testing to guide immunotherapy. In this study, we assess the suitability of EBUS-FNA cytology specimens for the testing of PD-L1.

Consecutive patients with Non-small cell lung cancer (NSCLC) underwent EBUS procedure between January 1, 2017 and March 31, 2018 for PD-L1 testing were included. The cell blocks of EBUS-FNA cytology specimens were used for PD-L1 testing using Dako 22C3 phamDx antibody according to the Dako protocol. PD-L1 protein expression in tumor cells is determined by using Tumor Proportion Score (TPS).

Of the 265 EBUS-FNA specimens from 262 patients sent for testing, 230 (86.8%) were adequate for PD-L1 testing. Of the 34 NSCLC patients with both histology and EBUS-FNA cytology specimens tested for PD-L1, the results from different specimen types had a concordance of 91.3%. The PD-L1 results from 16 paired specimens from the same anatomic site had 100% agreement. The rates of PD-L1 TPS ≥ 50% were significantly higher in the metastatic tumors in the lymph nodes than in the lung primary lesions. Therefore, EBUS-FNA cytology specimen is suitable for PD-L1 testing in patients with advanced NSCLC. The metastatic tumors in mediastinal lymph nodes appear to have higher PD-L1 expression than primary lesions.