S2545
Radiobiology - Microenvironment
ESTRO 2026
Results: Stromal enrichment, as defined by the ESTIMATE transcriptomic stromal gene signature optimal cut- point, results in significantly worse overall survival for MIBC patients treated with radiotherapy in the BC2001 trial (logrank p=0.0012, univariate hazard ratio = 1.67, 95% confidence interval = 1.22–2.29, stromal low reference) (Fig1A). In contrast, immune enrichment alone does not predict outcomes and should be considered in the context of CAFs. Multiplex imaging facilitated exploration of heterogenous CAF subtypes and revealed that stromal high samples had an enrichment of fibroblast activation protein (FAP)+ CAFs and dense extracellular matrix features, whereas stromal low samples were enriched for Podoplanin (PDPN)+ CAFs and vascular matrix structures (Fig1B).Spatial analysis revealed that CD8 T cells were frequently sequestered in the stroma with minimal invasion into tumour nests (n = 164 p=<2.2e-16) (Fig2). Moreover, CD8 T cells were most abundant in FAP enriched stromal neighbourhoods. Nearest neighbour analysis further highlighted spatially and functionally distinct subpopulations of FAP+ CAFs. A FAP+PDGFRa+ CAF, consistent with descriptions of inflammatory iCAFs, was in closest proximity to CD8 T cells, whereas FAP+aSMA+ myofibroblastic-like myCAFs, were proximal to tumour cells.
Mini-Oral 1161
Enrichment of fibroblast activation protein+ cancer-associated fibroblasts contributes to radiotherapy resistance in muscle-invasive bladder cancer Amy Burley 1 , Barry Gusterson 1 , Adrian Larkeryd 1 , Emma Westlund 2 , Tom Lund 3 , Alan Melcher 1 , Rik Bryan 4 , Ananya Choudhury 5 , Emma Hall 6 , Kelly Jones 7 , Shaista Hafeez 8 , Robert Huddart 8 , Nick James 1,8 , Anna Wilkins 1,8 1 Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, United Kingdom. 2 Light Microscopy Facility Sutton, The Institute of Cancer Research, London, United Kingdom. 3 Integrated Pathology Unit, Royal Marsden trust and The Institute of Cancer Research, London, United Kingdom. 4 Department of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom. 5 Division of Cancer Sciences, University of Manchester, Manchester, United Kingdom. 6 Clinical Trials and Statistics Unit, The Institute of Cancer Research, London, United Kingdom. 7 Bob Champion unit, Royal Marsden NHS Hospital Trust, London, United Kingdom. 8 Urology, Royal Marsden NHS Hospital Trust, London, United Kingdom Purpose/Objective: Radiotherapy is a radical bladder-preserving treatment option for patients with muscle-invasive bladder cancer, yet there are no biomarkers to predict radiotherapy responses. Cancer-associated fibroblasts (CAFs) are a key stromal population in the tumour microenvironment that contribute to radiotherapy resistance in pancreatic and rectal cancer [1, 2] however, their role in muscle-invasive bladder cancer is poorly characterised. To address the hypothesis that CAF enrichment contributes to poor radiotherapy outcomes in muscle-invasive bladder cancer (MIBC) we combined transcriptomic analysis with multiplex imaging and matrix fibre tracing to comprehensively characterise CAFs in the pre-treatment tumour
microenvironment. Material/Methods:
Transcriptomic data from BC2001 [3] was provided by Manchester University. Additional diagnostic tissue (n = 164) was collected from several bladder cancer cohorts: BCPP [4], RADIO (ISRCTN43698103), PLUMMB (NCT02560636) and COMB. RNA was profiled with Veracyte/Genewiz. Gene expression and survival analysis was completed in Rv4.4.0. Multiplex immunofluorescence images were generated using the Akoya Opal TSA system and PhenoImager HT, with quantification completed in Qupath v0.5.1. Spatial analysis was completed with MuSpAn [5]. Fibre tracing was conducted on Picrosirius red stained images with the Image J plug-in TWOMBLI [6] .
Made with FlippingBook - Share PDF online