ESTRO 2025 - Abstract Book

S3957

Radiobiology - Normal tissue radiobiology

ESTRO 2025

Clin Transl Radiat Oncol. 2024 Mar 13;46:100764. doi: 10.1016/j.ct 2/Treatment of Breast and Prostate Cancer by Hypofractionated Radiotherapy: Potential Risks and Benefits KJ Ray, NR Sibson, AE Kiltie Clin Oncol (R Coll Radiol). 2015 Jul;27(7):420–426. doi: 10.1016/j.clon.2015.02.008

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Digital Poster Effects of extremely low dose hyperthermia neutron irradiation on the immune function of healthy mice Ruiping Guo, Ran Peng, Zhuhui Yuan, Hao Wang Department of Radiation Oncology, Peking University Third Hospital, Beijing, China Purpose/Objective: Boron Neutron Capture Therapy (BNCT), utilizing high-linear energy transfer (LET) radiation, is widely recognized as a safe option for cancer patients. However, its impact on normal immune function under extremely low-dose conditions remains inadequately studied. This study aimed to evaluate the effects of extremely low-dose-rate hyperthermic neutron irradiation on systemic immune function, providing essential data for neutron radiation protection strategies. Material/Methods: Twenty-four female C57BL/6J mice (6–8 weeks old) were randomly assigned to four groups: the normal control group, 0.05 Gy irradiation group, 0.1 Gy irradiation group, and 0.25 Gy irradiation group. Each mouse received a retro-orbital injection of 2 mg 4-Borono-L-phenylalanine ( 10 B) 1.5 hours before undergoing total-body hyperthermic neutron irradiation. The mice were anesthetized and sacrificed on the day following two consecutive days of irradiation for four days. Peripheral blood and spleen samples were collected for routine hematological analysis and immune cell flow cytometry.

Results:

Compared with the control group, the peripheral blood leukocyte, neutrophil, and lymphocyte counts were significantly reduced across the 0.05 Gy, 0.1 Gy, and 0.25 Gy irradiation groups (all P <0.05, except neutrophils in the 0.25 Gy group). The most pronounced decrease was observed in the 0.05 Gy group. Splenic T cell numbers were significantly reduced following 0.05 Gy irradiation ( P <0.01), driven primarily by a decrease in CD4+ T cells ( P <0.05 in