S. Yuichi*a (Dr), W. Shinb (Dr), M. Hiroakib (Dr), I. Takayukib (Dr), Y. Yoshikanea (Dr), T. Nobumasab (Dr), S. Yoshihikob (Dr), I. Tomohikob (Dr), K. Masafumia (Prof), S. Yukinoria (Prof)

a Teikyo University School of Medicine, Tokyo, JAPAN ; b Saitama Cardiovascular and Respiratory Center, Saitama, JAPAN

* yuichi.saito@med.teikyo-u.ac.jp

Introduction The Dako PD-L1 immunohistochemistry (IHC) 22C3 pharmDx was approved by the US Food and Drug Administration, as a companion diagnostic test for pembrolizumab (Keytruda, Merk, Kenilworth, NJ, USA) in non-small cell lung cancer (NSCLC). Although increased PD-L1 expression levels can be associated with greater therapeutic efficacy of pembrolizumab, little is known about the concordance rate of PD-L1 expression between small biopsied specimen and surgically resected tumor tissue. Methods This was a prospective cohort study in single institute. Among surgical cases, patients with pathological nodal positive NSCLC were enrolled into this study. PD-L1 expression (22C3) was evaluated in preoperatively biopsied samples and tumor tissues from primary tumors and paired metastatic lymph nodes. All samples were formalin-fixed, and paraffin-embedded NSCLC tissues. Tumor cells which membrane exhibited complete or partial staining, were considered as PD-L1 positive. According to tumor proportion score (TPS), all samples were classified as no expression (TPS: <1%), low expression (TPS: 1-49%), or high expression (TPS: ≥50%). Results Primary tumors and paired metastatic lymph nodes were resected from 76 patients between August 2016 and April 2021 at Saitama Cardiovascular and Respiratory Center. Among of them, biopsied samples by preoperatively bronchoscopy were available in 18 cases. No expression was observed in 10 biopsied samples (55.6%), in 8 primary tumors (44.4%), and 11 metastatic lymph nodes (61.1%). Low expression was found in 6 biopsied samples (33.3%), in 4 primary tumors (22.2%), and 6 metastatic lymph nodes (33.3%). High expression was scored in 2 biopsied samples (11.1%), in 6 primary tumors (33.3%), and one metastatic lymph nodes (5.6%). The concordance rate was 0.389. CONCLUSIONS It is an important issue for physicians which tissue should be taken for treatment option, and further study is strongly expected to investigate it.

Disclosure of funding source(s):

Saitama Cardiovascular and Respiratory Center Grant (Number: 17ET, 18ET,  19ET, 20ET and 21FV)