Imaoka Tatsuhiko, Nishimura Mayumi, Daino Kazuhiro, Hosoki Ayaka, Takabatake Masaru, Kokubo Toshiaki, Doi Kazutaka, Showler Kaye, Nishimura Yukiko, Moriyama Hitomi, Morioka Takamitsu, Shimada Yoshiya, Kakinuma Shizuko
a Department of Radiation Effects Research, National Institute of Radiological Sciences (NIRS), National Institutes for Quantum and Radiological Science and Technology (QST), Chiba 263-8555, Japan.
d QST Advanced Study Laboratory, QST; Chiba 263-8555, Japan.
Radiat Res. 2017 Oct;188(4):419-425. doi: 10.1667/RR14829.1. Epub 2017 Aug 15.
The relative biological effectiveness (RBE) of neutrons depends on their physical nature (e.g., energy) and the biological context (e.g., end points, materials). From the perspective of radiological protection, age is an important biological context that influences radiation-related cancer risk, but very few studies have addressed its potential impact on neutron effects. We therefore investigated the influence of age on the effect of accelerator-generated fast neutrons (mean energy, ∼2 MeV) in an animal model of breast carcinogenesis. Female Sprague-Dawley rats at 1, 3 and 7 weeks of age were irradiated with fast neutrons at absorbed doses of 0.0485-0.97 Gy. All animals were kept under specific pathogen-free conditions and screened weekly for mammary tumors by palpation until they were 90 weeks old. Tumors were diagnosed based on histology. Mathematical modeling was used to analyze mammary cancer incidence, collectively using data from this study and a previously reported experiment on Cs gamma rays. The results indicate that neutron irradiation elevated the risk of palpable mammary carcinoma with a linear dose response, the slope of which depended on age at time of irradiation. The RBE of neutron radiation was 7.5 ± 3.4, 9.3 ± 3.5 and 26.1 ± 8.9 (mean ± SE) for animals exposed at 1, 3 and 7 weeks of age, respectively. Our results indicate that age of the animal is an important factor influencing the effect of fast neutrons on breast cancer risk.
中子的相对生物效应（RBE）取决于其物理性质（如能量）和生物学背景（如终点、材料）。从放射防护的角度来看，年龄是影响辐射相关癌症风险的一个重要生物学背景，但很少有研究探讨其对中子效应的潜在影响。因此，我们在乳腺癌发生的动物模型中研究了年龄对加速器产生的快中子（平均能量约2 MeV）效应的影响。对1、3和7周龄的雌性斯普拉格-道利大鼠进行快中子照射，吸收剂量为0.0485 - 0.97 Gy。所有动物均饲养在无特定病原体条件下，每周通过触诊筛查乳腺肿瘤，直至90周龄。根据组织学诊断肿瘤。使用数学模型分析乳腺癌发病率，综合使用本研究的数据和先前报道的关于铯γ射线的实验数据。结果表明，中子照射使可触及的乳腺癌风险呈线性剂量反应升高，其斜率取决于照射时的年龄。1、3和7周龄暴露动物的中子辐射RBE分别为7.5±3.4、9.3±3.5和26.1±8.9（平均值±标准误）。我们的结果表明，动物年龄是影响快中子对乳腺癌风险效应的一个重要因素。
