Reduced corneal toxicity following whole brain irradiation in mice

Year: 2026

Authors: Pillai V., Landi S., Uccheddu F., Di Martino F., Cavalieri A., Paiar F., Capaccioli S., Cicchi R., Costa M.

Autors Affiliation: Natl Res Council CNR, Inst Neurosci, Pisa, Italy; Univ Padua, Dept Ind Engn, Padua, Italy; Natl Inst Nucl Phys, Pisa, Italy; Univ Pisa, CISUP, Ctr Instrument Sharing, Pisa, Italy; Azienda Osped Univ Pisana, UO Fis Sanit, Pisa, Italy; Univ Pisa, Dept Phys E Fermi, Pisa, Italy; Univ Pisa, Dept Translat Res & New Technol Med & Surg, Pisa, Italy; Natl Inst Opt, Largo Enrico Fermi 6, I-50125 Florence, Italy.

Abstract: Purpose: The emergence of focal techniques such as stereotactic radiosurgery has led to a more selective use of whole brain radiotherapy (WBRT), yet it remains an important modality for treating diffuse or multiple intracranial malignancies. During WBRT, conventional dose rate radiotherapy (CONV-RT) inadvertently exposes ocular structures to radiation, potentially leading to vision-threatening complications. FLASH radiotherapy (FLASH-RT) delivers ultra-high dose rates in milliseconds, compared to CONV-RT where the dose delivery is over several minutes. This study employs 9 MeV electron beams to investigate whether FLASH-RT reduces radiation-induced corneal collagen damage relative to CONV-RT, using second-harmonic generation (SHG) imaging in a murine WBRT model. We hypothesized that FLASH-RT preferentially protects anterior ocular structures from incidental radiation damage compared to CONV-RT, potentially through preservation of extracellular matrix integrity and reduced damage to long-lived structural proteins. Materials and methods: C57BL/6 J wild type mice were divided into three experimental cohorts: untreated controls, FLASH-RT and CONV-RT. Within the radiotherapy cohorts, subgroups received a single whole-brain fraction of 10 Gy, 15 Gy or 20 Gy delivered at an average dose rate of 240 Gy/s for FLASH-RT or 0.1 Gy/s for CONV-RT. Corneal alterations were evaluated at acute (4 days) and chronic (40 days) post-irradiation timepoints. SHG microscopy quantified collagen organization using forward-to-backward (F/B) signal ratios and corneal thickness as markers of radiation-induced damage. Results: In the CONV-RT cohorts, we found significantly decreased F/B ratios compared to controls (p < 0.05), indicating substantial collagen disorganization, and increased corneal thickness indicative of radiation-induced tissue edema. Conversely, FLASH-RT was associated with higher F/B ratios and reduced corneal thickening compared with CONV-RT, indicating preservation of corneal extracellular matrix organization across both timepoints. However, the tissue sparing effect on corneal thickness was not sustained at the high single fraction threshold of 20 Gy. Conclusion: FLASH-RT preserves corneal collagen architecture compared to CONV-RT during whole brain irradiation, demonstrating significant potential for minimizing ocular toxicity in WBRT. These findings support clinical investigation of FLASH-RT as a tissue-sparing modality for brain cancer treatment. Journal/Review: CLINICAL AND TRANSLATIONAL RADIATION ONCOLOGY

Volume: 60      Pages from: 101235-1  to: 101235-9

More Information: This work was supported by Fondazione AIRC (IG 2024, ID 30434) ; the European Union NextGenerationEU through the PNRR MUR M4 C2 Inv. 1.5 projects ECS_00000017 (CUP: B83C22003930001) and UNIPI (CUP: I53C22000780001) ; and PRIN 2022PLNN4F. We also acknowledge Fondazione Pisa for supporting CPFR through grant no. 134/2021.
KeyWords: FLASH radiotherapy; Whole brain radiotherapy; Corneal toxicity; Second harmonic generation imaging; Radiation-induced damage; Collagen morphology
DOI: 10.1016/j.ctro.2026.101235