Elsevier

Clinical Lung Cancer

Volume 18, Issue 5, September 2017, Pages 527-534.e1
Clinical Lung Cancer

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

https://doi.org/10.1016/j.cllc.2016.12.002Get rights and content

Abstract

Background

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.

Methods

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.

Results

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.

Conclusion

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

Introduction

In recent years, progress has been made in the development of molecular targeted drugs in lung cancer.1, 2, 3, 4, 5, 6, 7, 8, 9 Therefore, identification of the tumor molecular characteristics is important for the management of the disease. Because most lung cancers are diagnosed at an advanced stage, we are frequently required to conduct molecular testing using a small amount of tumor tissue. To collect small amounts of tissue, transbronchial biopsy (TBB) has been conventionally performed.10, 11 Recently, endobronchial ultrasound-transbronchial needle aspiration (EBUS-TBNA) is emerging as a novel minimally invasive method for collecting greater amounts of tissue than TBB from mediastinal and hilar lymph nodes.12, 13, 14, 15, 16

A growing body of evidence suggests that immune checkpoint inhibitors, such as anti-programmed death-ligand 1 (PD-L1) antibodies, have been effective in several malignancies including lung cancer.17, 18, 19, 20, 21, 22 PD-L1 is an immune modulator that promotes immunosuppression by binding to programmed cell death-1 (PD-1) of T cells. PD-L1 expression on tumor cells has been suggested as a predictive marker of clinical response to anti-PD-L1 antibodies.19, 23, 24 Because PD-L1 expression needs to be evaluated only by immunohistochemistry (IHC), an adequate amount of tumor tissue is a prerequisite for the precise molecular characterization. Molecular characterization using small amounts of biopsy materials has been considered to be difficult owing to the limited number of tumor cells. To evaluate tumor PD-L1 expression by IHC, collecting enough tumor cells has been recommended.19

To the best of our knowledge, the number and morphologic intactness of tumor cells collected by small tissue sampling has never been investigated. As a primary analysis, we examined the number and crush rate of tumor cells in EBUS-TBNA samples and compared them with those of TBB to evaluate the potential usefulness of EBUS-TBNA as a method for the evaluation of PD-L1 expression.

Considering the intratumoral heterogeneity in lung cancer and the practical usefulness of EBUS-TBNA, we need to examine the PD-L1 positivity on tumor cells in EBUS-TBNA samples compared with that in the corresponding primary tumor.17, 18, 25 Although several studies have examined the concordance in PD-L1 positivity between biopsy and surgical samples, their results still remain inconclusive.25 Therefore, as a secondary analysis, we investigated the correlation of PD-L1 positivity between the biopsy samples and the corresponding surgical samples, to confirm the concordance between EBUS-TBNA materials and the primary tumor tissues.

Section snippets

Ascertainment of Cases

Our primary analysis was to evaluate the adequacy of EBUS-TBNA as an evaluation method of PD-L1 expression immunohistochemically, compared with TBB samples. Figure 1 shows the flow chart of case selection for this primary analysis. We performed EBUS-TBNA for 213 cases at The Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan, between January 1, 2013 and December 31, 2014. EBUS-TBNA was conducted for the purpose of initial diagnosis or screening for hilar and/or

Clinicopathologic Characteristics

As a primary analysis, we assessed the adequacy of 97 EBUS-TBNA samples to evaluate PD-L1 immunohistochemical expression and compared the results with 20 cases with TBB samples. Clinicopathologic characteristics of the 97 EBUS-TBNA cases and the 20 TBB cases are shown in Table 1, indicating that the features of the TBB subset were similar to the whole series.

The clinicopathologic characteristics of samples used for our secondary analyses are shown in Supplemental Table 1 (in the online

Discussion

We conducted this study to examine the feasibility of using EBUS-TBNA samples for the evaluation of tumor PD-L1 expression in lung cancer. We have shown that EBUS-TBNA is a more robust method than TBB in terms of the number and the morphologic intactness of collected tumor cells.

Preliminary trials have demonstrated that PD-L1 expression might be heterogeneous, thus indicating that small biopsies might not be suitable for the assessment of PD-L1 expression. Our study showed that EBUS-TBNA, TBB,

Disclosure

Y. Ishikawa received research grants from Daiichi Sankyo Co, Ltd and is a consultant for Fujirebio Inc. M. Nishio received research grants from Novartis Pharma Co, Ltd, Ono Pharma Co, Ltd, Chugai Pharma Co, Ltd, Pfizer Co, Ltd, Bristol-Myers Squibb Co, Ltd, Eli Lilly Co, Ltd, Taiho Pharma Co, Ltd, Astellas Pharma Co, Ltd, and AstraZeneca Co, Ltd, and is a consultant for Novartis Pharma Co, Ltd, Ono Pharma Co, Ltd, Chugai Pharma Co, Ltd, Eli Lilly Co, Ltd, Taiho Pharma Co, Ltd, Pfizer Co, Ltd,

Acknowledgments

The authors thank Mr Motoyoshi Iwakoshi, Ms Miyuki Kogure, Ms Tomoyo Kakita, Ms Kimie Nomura, and Ms Hiroko Nagano for their technical assistance and Ms Yuki Takano, Ms Chikako Yoshida, and Ms Yuka Toyama for their secretarial expertise. Parts of this study were supported financially by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan, including Grant Numbers 16K08679 (KI), 26430149 (HN), 15K08373 (NM), and 15H04714 (YI);

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