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Poster display session

1805 - PD-L1 immunohistochemistry (IHC) by three different assays and molecular profiling in tissue microarray (TMA) of gastric cancer

Date

09 Sep 2017

Session

Poster display session

Presenters

Yukiya Narita

Citation

Annals of Oncology (2017) 28 (suppl_5): v209-v268. 10.1093/annonc/mdx369

Authors

Y. Narita1, E. Sasaki2, Y. Yatabe2, K. Kato1, H. Okano1, S. Mitani1, K. Honda1, T. Masuishi1, H. Taniguchi1, S. Kadowaki1, T. Ura1, M. Ando1, M. Tajika3, S. Ito4, K. Muro1

Author affiliations

  • 1 Department Of Clinical Oncology, Aichi Cancer Center Hospital, 464-8681 - Nagoya/JP
  • 2 Department Of Pathology And Molecular Diagnostics, Aichi Cancer Center Hospital, 464-8681 - Nagoya/JP
  • 3 Department Of Endoscopy, Aichi Cancer Center Hospital, 464-8681 - Nagoya/JP
  • 4 Department Of Gastroenterological Surgery, Aichi Cancer Center Hospital, 4648681 - Nagoya/JP
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Resources

Abstract 1805

Background

Recent genomic and molecular characterization of gastric adenocarcinoma (GAC), such as Cancer Genome Atlas (TCGA), have shed light on the PD-L1 positivity and four different subtypes. Several PD-L1 IHC assays of scoring-criteria are developed in parallel. This study aimed to evaluate PD-L1 staining patterns and molecular profiling by TMA in GAC.

Methods

In total, 331 consecutive patients (pts) with GAC underwent curative surgery at Aichi Cancer Center Hospital between Jan 2009 and Dec 2010. Pts with no systemic chemotherapy before surgery and sufficient tumor content on the formalin-fixed and paraffin-embedded (FFPE) slides were eligible. EBV-encoded RNA in situ hybridization, IHC for deficient mismatch repair proteins (dMMR, MLH1/MSH2/MSH6/PMS2), HER2 and PD-L1 (22C3, 28-8, E1L3), and HER2 DISH were evaluated in TMA. Four cores of tumor tissue were punched out from individual FFPE tumor blocks and arrayed in a new TMA block. PD-L1 tumor positivity was categorized to ≥ 1%/≥25%/≥50% tumor cell membrane staining. Disease free survival (DFS) and overall survival (OS) were estimated by the Kaplan-Meier method.

Results

Among the cases, 226 pts were included in this study, excluding pts with prior chemotherapy (n = 26) and insufficient tumor samples (n = 79). Patient characteristics were as follows: male/female, 162/64; pStage (AJCC 7th ed.) I/II/III/IV, 100/39/58/29; EBV +/-, 13/213; proficient MMR/dMMR, 197/29, HER2 +/-, 24/202, and PD-L1 ≥1%/≥25%/≥50% (22C3 vs. 28-8 vs. E1L3), 11/4/2 vs. 7/6/6 vs. 12/10/8. Among 22C3, 28-8, and E1L3 assays, 94–97% of the pairs were concordant. PD-L1 positivity by all three assays was associated with EBV + (p 

Conclusions

The three tested PD-L1 assays did not show comparable staining patterns in all cases. Studies that correlate not only PD-L1 staining patterns but also EBV+/dMMR/HER2+ and response to immunotherapy are required to evaluate.Table:

676P

EBV+ N = 13EBV− N = 213PpMMR N = 197dMMR N = 29PHER2+ N = 24HER2− N = 202P
E1L3+ −3 109 2040.028 1914 250.060 2412 1900.62
28-8+ −3 104 209

Clinical trial identification

Legal entity responsible for the study

None

Funding

None

Disclosure

All authors have declared no conflicts of interest.

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