EBUS-TBNA as a Promising Method for the Evaluation of Tumor PD-L1 Expression in Lung Cancer

Because most lung cancers are diagnosed at advanced stages, we are forced to conduct molecular testing using small biopsy samples. Endobronchial ultrasound-transbronchial needle aspiration (EBUS-TBNA) is emerging as a minimally invasive biopsy technique. Here, we examined the usefulness of EBUS-TBNA to evaluate programmed death-ligand 1 (PD-L1) expression in lung cancer.

Using 97 consecutive cases of lung cancer diagnosed by EBUS-TBNA, from which 20 transbronchial biopsy (TBB) samples were available, we evaluated the number and morphological intactness of tumor cells in EBUS-TBNA and TBB samples. Additionally, given the intratumoral heterogeneity in primary lesions and the small sample size of biopsies, we also compared the tumor PD-L1 expression between the biopsy samples and the corresponding surgical materials.

EBUS-TBNA collected a significantly larger number of tumor cells than TBB (P < .001); the median number (interquartile range) of cells was 1149 (379-3334) in EBUS-TBNA and 435 (218-1085) in TBB. The crush rate in EBUS-TBNA was significantly lower than in TBB (P < .001). These showed the excellence of EBUS-TBNA. Additionally, PD-L1 positivity of EBUS-TBNA showed a good concordance with the corresponding primary tumor (r = 0.75; P = .086; n = 6) as well as with lymph node metastasis (r = 0.93; P = .02; n = 5). Moreover, PD-L1 positivity between EBUS-TBNA and TBB (n = 16), TBB and the corresponding primary tumor (n = 41), and lymph node metastasis and the corresponding primary tumor (n = 47) showed a moderate correlation (all r > 0.48; all P < .001), strengthening the potential concordance between EBUS-TBNA and primary tumor in PD-L1 positivity.

Our study suggests EBUS-TBNA as a promising method to evaluate PD-L1 expression in lung cancer.