ESTRO 2023 - Abstract Book

S2018

Digital Posters

ESTRO 2023

The immunophenotype of inflammatory cells did not show significant differences when compared to the lymphoid subpopulations in all time points. Inflammatory infiltrate consisted mainly of CD4-positive T-lymphocytes as compared with CD20-positive B-lymphocytes. The CD4/CD8 ratio’s were respectively 0.92, 0.75, 0.67, and 1.14 for each time point, and were no significant different between the time points (p=0,2). Conclusion Increased PD-L-1 immune expression is induced by HDR-brachytherapy in prostate cancer. Further analyses of the infiltrating T-cells will be presented. G. Mazzaschi 1 , M. Dos Santos 2 , P. Bergeron 1 , L. Sitterle 1 , M. Gerbé De Thoré 1 , W. Liu 1 , C. Clémenson 1 , L. Meziani 1 , A. Gonnelli 1 , O. Bawa 3 , A. Leroy 1 , R. Sun 1 , T. Henry 1 , P. Laurent 1 , L. Moron Dalla Tor 4 , F. Quaini 4 , M. Tiseo 5 , F. Milliat 2 , C. Robert 1 , M. Mondini 1 , E. Deutsch 6 1 Gustave Roussy, INSERM U1030, Paris, France; 2 Institute for Radiological Protection and Nuclear Safety (IRSN), Radiobiology and regenerative Medicine (SERAMED), Laboratory of Medical Radiobiology (LRMed), Paris, France; 3 Gustave Roussy, Plateforme de pathologie expérimentale et translationnelle, UMS AMMICA, Paris, France; 4 University of Parma, Medicine and Surgery, Parma, Italy; 5 University Hospital of Parma, Medicine and Surgery, Medical Oncology Unit, Parma, Italy; 6 Gustave Roussy, INSERM U1030 and Department of Radiation Oncology, Paris, France Purpose or Objective The ground-breaking results of immunotherapy (IT) in cancer patients still leave uncovered multiple drawbacks on the current clinical translation of cancer-immune interplay.By converting imaging data into high-throughput features, radiomics emerged as a non-invasive tool to decode tumor immune microenvironment (TIME) and predict IT response. Nonetheless, lack of standardization and methodological issues limit its clinical application. Scarce radiomic data in preclinical tumor settings have been generated so far. The aim of our study was to develop a µ CT-based radiomic platform in orthotopic murine models of head and neck cancer, to ultimately validate the biological reality of a radiomic approach in the evaluation of tumor infiltrating lymphocytes (TILs). Materials and Methods We established orthotopic models of head and neck cancer in immunocompetent mice. Tailored regimens including radiotherapy + selective antibodies were employed to modulate TIME (T cell enrichment vs depletion). In vivo preclinical imaging was performed using the Quantum FX µ CT technology; µ CT scans were processed for radiomic features (RFs) extraction (pyradiomics). Mice heads (comprising tumors) were collected and subjected to decalcification/inclusion protocol. Representative 5 µ m sections of the entire tumor area were cut from tissue block at constant distance of 500 µ m and immunohistochemically (IHC) stained for CD8 marker. A dedicated reconstruction algorithm was employed to generate a 3D map of CD8+ TILs ( Figure 1 ). PO-2243 Development of a µ CT radiomic platform to identify radio-immune signatures in murine tumor models

Results 1. Development and optimization of a quantitative µ CT imaging approach : we selected the best acquisition and reconstruction protocol able to minimize noise, improve spatial resolution and overcome potential miscalibration errors, thereby demonstrating the feasibility and reproducibility of µ CT imaging in murine models. 2. Deployment of a reproducible radiomic pipeline : after image pre-processing, including voxel resampling and image discretization, we delineated the volumes of interest (VOI) outlining the entire tumor region, which acted as source of information for quantitative analyses at tumor scale. Overall, 106 µ CT based RFs (shape, first- and second- order) were