Abdominal Flash Proton Irradiation Does Not Benefit the Intestine
Q ZHANG*, E Cascio, Q Yang, L Gerweck, P Huang, A McNamara, W Sung, J Schuemann, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA, Boston, MA
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TU-E-TRACK 5-1 (Tuesday, 7/27/2021) 3:30 PM - 4:30 PM [Eastern Time (GMT-4)]
Purpose: Abdominal Flash irradiation has been reported to spare the intestinal tissue, while some other reports suggested no gastrointestinal benefit was gained. In the present study, we plan to investigate the potential effect of Flash proton irradiation on the intestine.
Methods: A homogenous elliptical field of 1.2Í1.6 cm2 was obtained through the established Flash proton platform to cover 60~80% of the whole abdomen. The MRI scanning was conducted before irradiation and the mice were fixed on a designed holder to receive a single dose of 13.8 Gy, 16 Gy, 16.2 Gy, or 17.5 Gy. The dose rate of Flash irradiation was ~120 Gy/s and the one for the conventional dose rate (CDR) group was ~0.36 Gy/s. The Ki67 immunofluorescent staining of the intestine tissue was performed at 7 days and 14 days after irradiation. For the late effect, the mice were kept for as long as 210 days for the weight detection.
Results: Higher survival fraction of the mice was observed after 16 Gy conventional dose rate proton irradiation. There was no significant survival difference between the Flash and CDR groups after 17.5 Gy exposure. The Ki67 staining showed that the ratio of the proliferating cells in the crypts recovered at 7 days in both 13.8 Gy Flash and CDR groups. Compared with the 16.2 Gy CDR group, the long-term weight monitoring indicated more severe weight loss in the Flash group with the corresponding dose.
Conclusion: No benefit of Flash proton irradiation was gained after partial abdominal exposure. There should be some undiscovered physical and biological factors that impact the Flash effect on the intestine if it does exist.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by the Damon Runyon-Rachleff Innovation Award (DRR 57-19).
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