ESTRO 2025 - Abstract Book

S3951

Radiobiology - Normal tissue radiobiology

ESTRO 2025

References: 1. Landelijk Platform Protonentherapie (LPPT). Landelijk Indicatieprotocol Protonentherapie Hoofdhals versie 2.2. 2019. Available online: http://www.nvro.nl/publicaties/rapporten.  2. Vergouwe Y, Nieboer D, Oostenbrink R, Debray TPA, Murray GD, Kattan MW, Koffijberg H, Moons KGM, Steyerberg EW. A closed testing procedure to select an appropriate method for updating prediction models. Stat Med. 2017 Dec 10;36(28):4529-4539.

4064

Digital Poster expression of tenascin-c is upregulated in the early stages of radiation pneumonitis/fibrosis in a novel mouse model Kazuki Omori, Akinori Takada, Yutaka Toyomasu, Hajime Sakuma, Yoshihito Nomoto Radiology, Mie university, Tsu, Japan Purpose/Objective: The lung is a major dose-limiting organ for radiation therapy for cancer in the thoracic region, and the clarification of radiation-induced lung damage (RILD) is important. However, there have been few reports of animal experiment containing a detailed comparison of radiographic images with the pathological findings of radiation pneumonitis (RP)/radiation fibrosis (RF). We recently reported elevated expression of tenascin-C (TNC), an inflammation associated extracellular matrix molecule, in surgically resected lung tissue and serum in RILD patients. In this study, we have developed a novel mouse model of partial lung irradiation and studied it with special attention paid to the computed tomography (CT) images and immunohistological findings. Material/Methods: We have developed a novel radiation shielding device that allows partial irradiation of the lung of mice. The right lungs of BALB/c mice were irradiated locally at 30 Gy/1fr, and the following two groups were created. In Group 1, sequential CT was performed from 12 to 32 weeks post-irradiation to confirm the time-dependent changes in RILD. In Group 2, the CT images and histopathological findings of the lung were compared from 12 to 44 weeks post irradiation. Results: In Group 1, RP findings (ground-glass opacity, pulmonary infiltrate) were observed on the CT images from 20 weeks after irradiation. By 24 and 28 weeks, RP findings were expanded and more distinct. At 32 weeks, the lung shadow changed from RP to RF (consolidation with volume loss). In Group 2, H-E staining showed an infiltrate of inflammatory cells suggestive of RP was observed in hematoxylin and eosin (H-E) staining at 16 weeks after irradiation, whereas the CT images did not show specific findings. At 20 weeks, the marked RP findings were confirmed by CT images and H-E staining. As the CT findings changed from RP to RF, decreasing inflammatory cells and increasing collagen deposition and the progression of alveoli destruction were observed in histologically. TNC was expressed at 16 weeks, earlier than the changes observed with the CT images. The expression of TNC was peaked at 20 weeks and subsequently decreased. Conclusion: We developed a new mouse model of RILD and performed long-term imaging and a pathological evaluation. Furthermore, we evaluated the relationship between TNC and RILD, suggesting that TNC is a useful inflammatory marker.

Keywords: radiation pneumonitis, mice, tenascin-C