Concordance of PD-L1 combined positive score (CPS) analysis between primary gastric cancer and matched peritoneal metastasis.

• DOI: 10.1200/jco.2024.42.16_suppl.e16068
• Publication Date: 2024-07-02T01:30:41Z
• Authors: Valentina Massa; Francesca Salani; Giada Grelli; Virginia Genovesi; Caterina Vivaldi; Francesca Signorini; Clara Ugolini; Maria Elena Filice; Laura Bernardini; Silvia Cesario; Miriam Caccese; Jessica Graziani; Linda Bartalini; Dario Berra; Francesco Mangogna; Vincenzo Nardini; Gianluca Masi; Lorenzo Fornaro
• Keywords: Concordance

e16068 Background: Peritoneum represents one of the most common metastatic sites gastroesophageal adenocarcinoma (GEA) and is associated with poor prognosis. Programmed death-ligand 1 (PD-L1) expression a recognized predictive biomarker response to immune checkpoint inhibitors (ICIs) in first-line setting. However, data from pivotal trials showed poorer clinical efficacy ICIs sub-set patients peritoneal involvement, regardless PD-L1 score magnitude. Here, we investigated temporal spatial heterogeneity between primary tumor matched metastasis. Methods: according CPS was determined by immunohistochemistry using VENTANA (SP263) assays on formalin-fixed paraffin-embedded (FFPE) tissues derived 22 treated at our institution for advanced GEA September 2015 August 2023. Concordance rate metastasis cut-off 5 reported (spatial heterogeneity); additionally, concordance value before after administration systemic treatments analyzed (temporal heterogeneity). Results: 12(54.5%)/5(22.7%) samples 12(54.5%)/1(4.5%) metastases ≥ 1/ 5, respectively. specimens 54.5% 72.7% cuts-off respectively, highlighting marked heterogeneity. High (94%) negative metastases, against 5; contrast, none positive retained peritoneum. Evident also observed, 56% pre- versus post-treatment comparison. Conclusions: characterized which more prominent lower cut-offs values. This evidence could hamper its role as ICIs. The high intra-patient discordance suggests that should not be recommended preferred source assessment.