Ovarian tumours in mice after X-ray and neutron exposure

Purpose: To determine the dose relationship and RBE for ovarian murine tumors after X-ray and neutron exposure.

Status: 1982 - 1987, terminated, data in ERAD

Treatment: Single acute exposure to 250 kVp X-rays (1.5 mm HVL, 60 mGy/min) or 1.5 MeV neutrons from a van de Graaff accelerator at the JRC Ispra (1.83 mGy/min)

Dosimetry: Twin ionization chamber method, ENDIP

Endpoints: Life-span study (spontaneous death) with macroscopic/microscopic pathology

Animal: Female (C57Bl/Cne x C3H/Cne)F1 (BC3F1) mice aged 3 months

Results: A significant increase in life-shortening was observed for single neutron exposure to 0.08 Gy. or more. Assuming a linear non-threshold dose-effect relationship, the RBE value is 12.3 for 1.5 MeV neutrons. A statistically significant increase in solid tumors is seen for single neutron exposure from 0.08 Gy and for X-ray exposure from 1 Gy. The data for neutrons at low doses can be fitted to a linear dose effect relationship. A separate analysis of of ovarian tumor induction substantiates the hypothesis of a threshold for X-rays, whereas such a threshold is not evident for neutrons. A trend analysis confirms these findings. When death rates are analyzed, a general agreement between their shift to earlier times and tumor induction was found.

研究目的：探究X射线与中子照射后，小鼠卵巢肿瘤的剂量效应关系及相对生物效能（Relative Biological Effectiveness, RBE）。
研究状态：1982年至1987年开展，已结题，相关数据存储于ERAD数据库。
照射方案：采用欧洲联合研究中心埃斯普拉特分中心（JRC Ispra）范德格拉夫加速器产生的250 kV X射线（半值层1.5 mm，剂量率60 mGy/min）或1.5 MeV中子进行单次急性照射，其中中子照射的剂量率为1.83 mGy/min。
剂量测定：采用双电离室法及ENDIP技术。
观测终点：以自发性死亡为研究终点的寿命实验，并辅以大体病理学与显微病理学检测。
实验动物：3月龄雌性（C57Bl/Cne × C3H/Cne）F1（简称BC3F1）小鼠。
实验结果：单次中子照射剂量≥0.08 Gy时，小鼠寿命显著缩短。在线性无阈值剂量效应模型假设下，1.5 MeV中子的相对生物效能（RBE）为12.3。单次中子照射剂量≥0.08 Gy、X射线照射剂量≥1 Gy时，实体瘤发生率均出现具有统计学意义的显著升高。低剂量中子照射数据可拟合为线性剂量效应关系。针对卵巢肿瘤诱导的独立分析证实，X射线照射存在剂量阈值，而中子照射未表现出明显阈值。趋势分析验证了上述结论。对死亡率的分析显示，死亡时间提前与肿瘤诱导之间存在总体一致性。