Department of Physics, Science Faculty, University of Zürich, Zürich, Switzerland; Radiotherapy Hirslanden, Witellikerstrasse 40, 8032 Zürich, Switzerland.
Department of Physics, Science Faculty, University of Zürich, Zürich, Switzerland.
Phys Med. 2017 Oct;42:228-231. doi: 10.1016/j.ejmp.2017.03.011. Epub 2017 Mar 28.
Epidemiological studies of long term radiotherapy survivors provide useful insights into dose-response relationships for secondary cancer induction risk at high doses. There are uncertainties involved in estimating the dose to the location of the second malignancy, because the dose distributions in radiotherapy patients can be spatially highly heterogeneous and the size of the diagnosed tumor is on the order of a few cm. Therefor it is nearly impossible to obtain the exact dose corresponding to the exact tumor induction location and so organ specific dose-response relationships have large errors not only in the reported risk, but also in the estimated dose. In this work two alternative methods are proposed for future applications involving investigations into dose response relationships for second cancer induction risk, the method of organ sub-division and the method of risk equivalent dose. The method of organ sub-division takes the inevitable inhomogeneous dose distribution into account by applying epidemiological methods to organ sub-divisions which have a nearly homogenous dose. The method of risk equivalent dose combines risk modeling and epidemiological data analysis. Risk models can be optimized by using an iterative procedure assuming a variation of organ specific dose-responses. The advantage of the alternative methods is that the inhomogeneity of the dose in the organs at risk is taken into account. The second method has the additional advantage that the dose to the location of the tumor site must not be known and that epidemiologically obtained risks that were not stratified by organ specific risk can be used.
长期放射治疗幸存者的流行病学研究为高剂量继发癌症诱导风险的剂量反应关系提供了有用的见解。由于放射治疗患者的剂量分布可能在空间上高度不均匀，并且诊断出的肿瘤大小约为几厘米，因此估计第二恶性肿瘤位置的剂量存在不确定性。因此，几乎不可能获得与确切肿瘤诱导位置相对应的确切剂量，因此器官特异性剂量反应关系不仅在报告的风险中，而且在估计的剂量中都存在较大误差。在这项工作中，提出了两种替代方法，用于未来涉及调查继发癌症诱导风险的剂量反应关系的应用，即器官细分方法和风险等效剂量方法。器官细分方法通过将流行病学方法应用于具有几乎均匀剂量的器官细分部分来考虑不可避免的不均匀剂量分布。风险等效剂量方法结合了风险建模和流行病学数据分析。可以通过使用假设器官特异性剂量反应变化的迭代过程来优化风险模型。替代方法的优点是考虑了风险器官中剂量的不均匀性。第二种方法的额外优点是不必知道肿瘤部位的剂量，并且可以使用未按器官特异性风险分层的流行病学获得的风险。
