Comparative Study of PD-L1 Status between Surgically Resected Specimens and Matched Biopsies of Gastric Cancer Reveal Major Discordances: A Potential Issue for Anti-PD-L1 Therapeutic Strategies

Comparative Study of PD-L1 Status between Surgically Resected Specimens and Matched Biopsies of Gastric Cancer Reveal Major Discordances: A Potential Issue for Anti-PD-L1 Therapeutic Strategies

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Corresponding Author
Soo Hee Kim
Pathology Center, Seegene Medical Foundation, Seoul, Korea

A B S T R A C T

Background: Inhibitors of programmed death-ligand 1 (PD-L1) have potential therapeutic value in gastric cancer. We investigated PD-L1 expression patterns in paired biopsy and resection specimens. Patients and Methods: Thirty-nine formalin-fixed, paraffin-embedded paired samples were assessed using PD-L1 22C3 pharmDx immunohistochemistry technique. Combined positive score (CPS) was calculated as the ratio of PD-L1 stained cells (tumor cells, lymphocytes, and macrophages) to the total number of viable tumor cells, multiplied by 100. The CPS ≥1 indicated PD-L1 positivity. Results: PD-L1 positivity was evident for 33 (84.6%) of 39 resection cases; all displayed low positivity (1≤CPS<50). Only 10 (30.3%) of 33 positive cases in the resection specimens had simultaneous PD-L1 positivity in the paired biopsy specimens; two cases displayed high positivity (CPS 50 and 70) and eight displayed low positivity (1≤CPS≤50). Among the 29 negative cases with biopsy specimens, 23 (79.3%) displayed PD-L1 low positivity in the paired resection specimens and only six had concordant negativity in both specimens with poor agreement (concordance rate 41.0%, k value = 0.118, correlation coefficient 0.234; p=0.152). All the high microsatellite instability cases had concordant PD-L1 positivity in resection and biopsy specimens. Conclusions: There was relatively poor agreement of PD-L1 expression between biopsy and resected tumor specimens. The biopsy specimens underestimated the PD-L1 status observed for the total resected samples. This indicates the necessity of obtaining multiple biopsies from different areas of the tumor to enhance the validity and reliability of PD-L1 analysis.

Article Info

Article Type
Original Article
Publication history
Received: Sat 11, Jan 2020
Accepted: Wed 29, Jan 2020
Published: Fri 31, Jan 2020
Copyright
© 2023 Soo Hee Kim. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Hosting by Science Repository.
DOI: 10.31487/j.COR.2020.01.06