1226P Predicting benefit from maintenance durvalumab after first-line chemotherapy (1L CTx) in oesophagogastric adenocarcinoma (OGA) using a novel tumour microenvironment (TME) RNA-based assay

Abstract

Immune checkpoint inhibitors (ICI) are efficacious in subsets of OGA but predictive biomarkers beyond MMR and PD-L1 status are needed. Results from a phase II, multicentre, randomised, adaptive study (PLATFORM) showed that maintenance durvalumab (A3) did not prolong progression free or overall survival (PFS or OS) after platinum-fluoropyrimidine 1L CTx over surveillance (A1) in HER2 negative OGA. The Xerna™ TME RNA panel uses ≈100 genes to classify the TME along an immune and angiogenic axis into Angiogenic (A), Immune Active (IA), Immune Desert (ID) and Immune Suppressed (IS) phenotypes.