ESTRO 2025 - Abstract Book

S3923

Radiobiology - Normal tissue radiobiology

ESTRO 2025

Conclusion: We developed multiple machine learning models to sHT after radiotherapy using pituitary and thyroid radiomics/dosiomics features. The combined model achieved an AUC of 0.855, demonstrating the predictive value of complementary information from both thyroid and pituitary as well as CT and dose.

Keywords: Hypothyroidism, Radiomics, Pituitary

References: Chow JCH,et al. Post-radiation primary hypothyroidism in patients with head and neck cancer: External validation of thyroid gland dose–volume constraints with long-term endocrine outcomes. Radiother Oncol. 2022;177:105–10. doi:10.1016/j.radonc.2022.10.034. 2258 Poster Discussion The impact of vitreous humor: a new perspective on radiation-induced cataractogenesis Ecem Yigit 1 , Irem Koc 2 , Gozde Yazici 1 , Ekim Gumeler 3 , Aysenur Elmali 4 , Alper Kahvecioglu 1 , Yagiz Yedekci 1 , Samiye Yabanoglu Ciftci 5 , Meltem Karatas 6 , Aysima Sezer 5 , Hayyam Kiratli 2 , Mustafa Cengiz 1 1 Radiation Oncology, Hacettepe University, Faculty of Medicine, Ankara, Turkey. 2 Ophthalmology, Hacettepe University, Faculty of Medicine, Ankara, Turkey. 3 Radiology, Hacettepe University, Faculty of Medicine, Ankara, Turkey. 4 Radiation Oncology, Baskent University, Faculty of Medicine, Ankara, Turkey. 5 Biochemistry, Hacettepe University, Faculty of Pharmacy, Ankara, Turkey. 6 Radiology, Bilkent University, Ankara, Turkey Purpose/Objective: The mechanisms underlying radiation-induced cataract pathogenesis are not yet fully elucidated, though oxidative stress is recognized as a key factor in cataractogenesis. The vitreous humor plays a critical role in preserving the lens's hypoxic environment by regulating oxygen levels and providing antioxidants. This study investigates the impact of radiation-induced alterations in the vitreous humor on lens health, with a focus on its potential to induce cataracts. Material/Methods: This experimental study involved 12 New Zealand rabbits. A single dose of 20 Gy radiation was delivered to the vitreous humor of the left eye using a lens-sparing technique, while the right eye served as a control. Monthly ophthalmological assessments were performed over three months. At the end of the study, orbital magnetic resonance imaging (MRI) was conducted, and vitreous humor samples were analyzed spectrophotometrically to measure total oxidant and antioxidant levels. Results: In the treatment plan, the left vitreous received a mean dose of 18.3 Gy, while the left lens was exposed to a D mean of 1.5 Gy and a D max of 9.5 Gy. Cataract formation was observed in two of the eight irradiated eyes (25%). MRI findings revealed a significant decrease in signal intensity in the left eye’s aqueous humor in non-contrast sequences (p = 0.03) and an increase in signal intensity in late post-contrast sequences (p = 0.04). Spectrophotometric analysis showed significantly reduced total oxidant levels (p = 0.04) and oxidative stress index