P2.02-072 Reliability of Small Biopsy Samples for Tumor PD-L1 Expression in Non-Small-Cell Lung Cancer

Abstract

Programmed death 1 immune checkpoint inhibitor antibody has been effective in patients with PD-L1 positive advanced NSCLC. However, surgically resected specimens or core-needle biopsy samples were used to estimate drug potency in past clinical trials. The aim of this study is to prospectively investigate small sample reliability for NSCLC to determine the PD-L1 expression status. We prospectively enrolled patients who underwent diagnostic biopsy by any procedures (under rigid bronchoscopy, flexible bronchoscopy, CT & US-guided core-needle, excisional method) from March 2017 to March 2018 (ongoing study). Pathologically confirmed non-small cell lung cancer (NSCLC), PD-L1 expression was evaluated in our institution using companion diagnostic PD-L1 immunohistochemistry：PD-L1 IHC 22C3 pharmDx (Daco) with autostainer Link 48, detecting a driver mutation in parallel. We evaluated: 1) the total number of tumor cells and sample size; 2) compared PD-L1 expression for each procedure using tumor proportion score: TPS (<1%, 1～49%, 50%≤), 3) the concordance rate of PD-L1 expression status by biopsy and surgical materials; and 4) the efficacy of administration for PD-1 immune checkpoint inhibitor antibody. During the first three months 44 cases of PD-L1 expression were evaluated. 33 cases were sampled by bronchoscopy (6 under rigid scope with BF 1T260, 17 TBBs using 1T260/P260F in 4/13 cases, 10 TBNAs), and 7 cases were CT-guided core-needle biopsy. The TPS (<1%, 1～49%, 50%≤) was 8/6/10 for TBB, 3/4/2 for TBNA, and 4/0/3 for CT-guided. Four cases harboring EGFR mutation showed a lower PD-L1 expression (<10%). Utilizing smaller samples to evaluate PD-L1 expression, and the frequency of TPS were comparable to past clinical trials using larger samples. Smaller samples might be an accurate alternative to assess PD-L1 expression. Current data will be updated at the conference.