ESTRO 2025 - Abstract Book

S3899

Radiobiology - Microenvironment

ESTRO 2025

multiplexed tissue imaging in resectable ESCC patients underwent neoadjuvant PD-1 blockade treatment combined with radiotherapy.

Material/Methods: Phenocycler multiplexed tissue imaging was performed with 28 markers in pre- and post-treatment tissues from 5 pathological complete response (pCR; 0% residual viable tumor) and 5 relatively resistant (≥60% residual viable tumor) ESCC patients. The images were then processed in Qupath and Stardist was used to do cell segmentation. The detection measurements of each marker and the X- and Y-coordinate of each cells were exported and further analyzed with Seurat. 18 cell types were identified and cell proportion difference was calculated between pCR and resistant patients. Spatial distance between cell types were calculated and Scimap was used to do the Cellular Neighbourhood (CN) analysis. SpatialScore analysis was done to compare the distance between 3 cell-types which included immune suppression cells, immune activated immune cells, and tumor cells. Single cell RNA (sc-RNA) sequencing data were used to analyze the feature of myeloid cells in ESCC patients. Results: In pre-treatment samples, the proportion of CD8+ T were lower while exhausted T and T regulating cells (Tregs) were higher in resistant patients than pCR patients. CNs in residual tumor invasion margin after treatment contained abundant myeloid cells and Ki-67 high epithelial cells. Spatial distance analysis showed that in resistant patients, CD15+ myeloid cells showed a shorter distance to CD8+ T cells and SpatialScore analysis further showed that the minimal distance between CD15+ myeloid cells and CD8+ T cells was shorter than distance between Ki-67 high epithelial cells and CD8 + T cells. Based on our previous finding, CD15+ myeloid derived suppressor cells showed upregulated P2RX4 expression after radiation. P2RX4+ myeloid cells highly expressed neutrophil extracellular traps (NETs) score. More NETs were formed in resistant patients then pCR patients after treatment. Conclusion: Collectively, we provide an approach for investigating the underlying mechanism of the resistance to neoadjuvant PD-1 blockade treatment combined with radiotherapy in resectable ESCC by spatial omics. Mini-Oral Micro-physio/pathological system on-chip as a preclinical model to replicate pancreatic tumor microenvironment for radiobiological applications Sofia Tartaro 1 , Alessia Beretta 2 , Dalila Petta 3 , Silvia Redaelli 4 , Nadia Zaffaroni 2 , Chiara Arrigoni 3 , Sandro Pasquali 5 , Matteo Moretti 6 , Tiziana Rancati 1 , Luca Possenti 1 1 Data Science Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy. 2 Molecular Pharmacology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy. 3 Service of Orthopaedics and Traumatology, Ente Ospedaliero Cantonale, Regenerative Medicine Technologies Lab, Bellinzona, Switzerland. 4 Experimental Oncology, Fondazione IRCCS Istituto Nazionaledei Tumori, Milan, Italy. 5 Molecular Pharmacology Unit, Fondazione IRCCS Istituto Nazionaledei Tumori, Milan, Italy. 6 Service of Orthopaedics and Traumatology, Ente Ospedaliero Cantonale, Regenerative Medicine Technologies Lab, Bellizona, Switzerland Purpose/Objective: Pancreatic cancer is a leading cause of neoplastic death, with a 5-year survival rate of 13% [1]. Pancreatic ductal adenocarcinoma (PDAC) comprises over 90% of histological subtypes and is frequently associated with a hypoxic desmoplastic microenvironment rich in a dense fibrotic stroma [2]. Pancreatic Stellate Cells (PSCs) are central contributors to tumour progression. Such a peculiar microenvironment affects treatment outcomes, altering drug Keywords: Immunotherapy, spatial omics, ESCC 2975