1900P - Real-world prospective data of small biopsy samples for tumor PD-L1 expression in non-small cell lung cancer

Abstract

Background: PD-1 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. Methods: The aim 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 (bronchoscopy, CT/US-guided core-needle) from 2017.3 to 2018.3. Pathologically confirmed NSCLC PD-L1 expression was evaluated in our institution using companion diagnostic PD-L1 IHC. 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 (50%≦, 1∼49%, <1%), 3) the concordance rate of PD-L1 expression status by biopsy and surgical materials. Results: 137 cases of PD-L1 expression were evaluated. 112 cases were sampled by bronchoscopy (98 TBBs using BF-1T260/P260F in 23/75 cases, 20 TBNAs), and 25 cases of CT or US-guided core-needle biopsy. The TPS (50%≦ / 1∼49% / <1% / undiagnosed) for total cases was 31/29/37/3% respectively which was similar to the past report. In histological subtype, TPS for adenocarcinoma (n = 82) were 28/27/43/2% and squamous cell carcinoma (n = 49) were 35/35/27/4% respectively. TPS for TBBs using BF-P260F (thin bronchoscopy) were 20/33/43/4% and TBBs using BF-1T260 (normal bronchoscopy) were 48/22/30/0%. TPS for TBNAs were 50/25/25/0% and CT or US-guided sample showed 37/21/37/5%. Four cases were not able to be diagnosed for TPS because we couldn’t obtain enough tumor cells (less than 100 tumor cells) for diagnosis of TPS. The concordance rate of PD-L1 expression status by biopsy and surgical materials was 83.3% for comparison of 24 cases. Conclusions: Utilizing smaller samples to evaluate PD-L1 expression, the frequencies of TPS were comparable to past clinical trials which used larger samples for evaluating TPS. In this study, the larger samples showed higher PD-L1 expression than smaller samples due to their containing more squamous cell carcinoma cases or advanced stage. The concordance rate of PD-L1 expression for surgically resected tissue and biopsy sample was relatively good in our institution. Clinical trial identification: UMIN000027030. Legal entity responsible for the study: Kei Morikawa. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.