ESTRO 2025 - Abstract Book

S3947

Radiobiology - Normal tissue radiobiology

ESTRO 2025

Amaechi BT, Higham SM, Edgar WM (1999) Techniques for the production of dental eroded lesions in vitro. J Oral Rehabil 26(2):97–102 Arid J, Palma-Dibb RG, de Oliveira HF, Nelson-Filho P, de Carvalho FK, da Silva LAB, de Siqueira Mellara T, da Silva RAB, Faraoni JJ, de Queiroz AM. Radiotherapy impairs adhesive bonding in permanent teeth. Support Care Cancer. 2020 Jan;28(1):239-247 Austin RS, Giusca CL, Macaulay G, Moazzez R, Bartlett DW. Confocal laser scanning microscopy and area-scale analysis used to quantify enamel surface textural changes from citric acid demineralization and salivary remineralization in vitro. Dent Mater. 2016 Feb;32(2):278-84

3739

Digital Poster Microbeam Radiotherapy in Liver Tissue: Radiobiological Insights into Mechanisms of Normal Tissue Sparing Cheuk Ting Wu 1 , Jennifer Fazzari 2 , Verdiana Trappetti 1 , Cristian Fernandez-Palomo 1 , Paolo Pellicioli 1 , Valentin Djonov 1 1 Institute of Anatomy, University of Bern, Bern, Switzerland. 2 Department of Radiation Oncology, Mayo Clinic, Rochester, USA Purpose/Objective: Liver cancer, predominantly hepatocellular carcinoma (HCC), poses challenges for conventional radiotherapy (RT) due to the risk of radiation-induced liver disease. Spatially Fractionated Radiation Therapy (SFRT), including Microbeam Radiotherapy (MRT), has demonstrated complete tumour responses in glioma and melanoma models 1,2 and promising normal tissue sparing effects 3 . This study investigates the normal tissue sparing effects of MRT and its underlying mechanisms in liver tissue, with the goal of exploring its therapeutic potential for HCC. Material/Methods: C57BL/6J mice were partially irradiated using MRT at the European Synchrotron Radiation Facility (ESRF) and the Australian Synchrotron (ANSTO). Beam geometry was defined by 50 µm width and 400 µm spacing (centre-to centre). Peak doses of 400 Gy were delivered at dose rates of ~14,000 Gy/s (ESRF) and ~1,000 Gy/s (ANSTO). Liver tissues were collected at multiple timepoints for immunohistochemical analysis. Ongoing investigations employ Imaging Mass Cytometry (IMC) to characterize immune cell dynamics and microenvironmental changes. Results: Immunohistochemistry revealed significant cell death (TUNEL, γH2AX) localized along beam paths at 24–48 hours post-MRT, with active proliferation (Ki67) and macrophage infiltration (F4/80) observed at 48 hours 3 , suggesting active turnover of radiation-damaged cells and regeneration. Serum alanine aminotransferase (ALT) levels exhibited a mild (<2-fold) increase, indicating minimal liver injury. Long-term evaluation (6 months post-MRT) showed no fibrosis, emphasizing the tissue-sparing effects of MRT.