Little M P, Muirhead C R
National Radiological Protection Board, Chilton, UK.
Int J Radiat Biol. 1996 Jul;70(1):83-94. doi: 10.1080/095530096145364.
The recently released data on cancer incidence in the Japanese atomic bomb survivors are analysed using a variety of relative risk models which take account of errors in estimates of dose to assess the dose-response at low doses. For all solid cancers analysed together there is a significant positive dose-response (at the one-sided 2.5% significance level) if all survivors who received < 0.5 Sv are considered, but the significance vanishes if doses of < 0.2 Sv are considered. If a relative risk model with a threshold (the dose-response being assumed linear above the threshold) is fitted to the solid cancer data, a threshold of more than about 0.2 Sv is inconsistent with the data, whereas these data are consistent with there being no threshold. Linear-quadratic models and linear-quadratic models with an exponential cell-sterilization term provide no better fit than the linear model. For the three main radiation-inducible leukaemia subtypes analysed together (acute lymphatic leukaemia, acute myeloid leukaemia and chronic myeloid leukaemia) there is a significant positive dose-response (at the one-sided 2.5% significance level) if all survivors who received < 0.5 Sv are considered, but the significance vanishes if doses of < 0.2 Sv are considered. If a relative risk model with a threshold (the dose-response being assumed linear above the threshold) is fitted to the leukaemia data, a thresh-old of more than about 0.3 Sv is inconsistent with the data. In contrast with the solid cancer data, the best estimate for the threshold level in the leukaemia data is significantly different from zero, even when allowance is made for a possible quadratic term in the dose-response, albeit at borderline levels of statistical significance (p = 0.04). There is little evidence for curvature in the leukaemia dose-response from 0.2 Sv upwards. However, the possible underestimation of the errors in the estimates of the dose threshold as a result of confounding and uncertainties not taken into account in the analysis, together with the lack of biological plausibility of a threshold, makes the interpretation of this finding questionable.
利用各种相对风险模型对最近公布的日本原子弹幸存者癌症发病率数据进行了分析，这些模型考虑了剂量估计中的误差，以评估低剂量下的剂量反应。对于所有一起分析的实体癌，如果考虑所有接受剂量小于0.5 Sv的幸存者，则存在显著的正剂量反应（在单侧2.5%显著性水平），但如果考虑剂量小于0.2 Sv，则显著性消失。如果将具有阈值的相对风险模型（假设阈值以上剂量反应呈线性）应用于实体癌数据，阈值大于约0.2 Sv与数据不一致，而这些数据与无阈值一致。线性二次模型和带有指数细胞失活项的线性二次模型并不比线性模型拟合得更好。对于一起分析的三种主要辐射诱导白血病亚型（急性淋巴细胞白血病、急性髓细胞白血病和慢性髓细胞白血病），如果考虑所有接受剂量小于0.5 Sv的幸存者，则存在显著的正剂量反应（在单侧2.5%显著性水平），但如果考虑剂量小于0.2 Sv，则显著性消失。如果将具有阈值的相对风险模型（假设阈值以上剂量反应呈线性）应用于白血病数据，阈值大于约0.3 Sv与数据不一致。与实体癌数据相反，白血病数据中阈值水平的最佳估计值与零有显著差异，即使在剂量反应中考虑了可能的二次项，尽管在统计显著性的临界水平（p = 0.04）。从0.2 Sv以上，白血病剂量反应几乎没有曲率的证据。然而，由于分析中未考虑的混杂因素和不确定性，可能低估了剂量阈值估计中的误差，再加上阈值缺乏生物学合理性，使得这一发现的解释存在疑问。
