Comparison of the secondary cancer risk after conventional and intensity-modulated radiotherapy using an animal model

外射束放射治疗是当前多模式癌症治疗的组成部分。在过去的几十年中，通过提高靶区的适形性来减少辐射引起的不良反应，这是由调强放射治疗（IMRT）的出现所实现的。然而，为了实现高度的适形性，该技术以低辐射剂量暴露身体的显著体积，这通常被称为“低剂量浴”。据推测，调强放射治疗可能因此增加继发性癌症，这是有争议的讨论，因为迄今为止没有或很少有实验（标准化）数据的发病率继发性癌症在低剂量地区。我们的小组已经委托了一个微型CT作为小动物照射设备，作为该提案的第一步，我们现在的目标是建立一个基于蒙特-卡罗的计划系统，使小动物IMRT。然后，我们将在肿瘤允许大鼠中定义一个固定的靶体积，该靶体积将以常规方式（通过相反的场）或通过强度调制方式的旋转进行照射。主要目的是比较高剂量、低剂量和无剂量地区的诱发肿瘤发生率。第二个目标是建立总体和无癌生存率。该项目展示了常规和调制放射治疗后癌症发病率的第一次标准化比较评估，并将为重新评估与该技术相关的风险提供数据。

External-beam radiotherapy is an integral part of current multimodal cancer therapies. Over the past decades, radiation-induced adverse effects were consequently reduced by improving target coverage with higher conformality, which was enabled by the advent of intensity-modulated Radiotherapy (IMRT). However, to achieve a high degree of conformality, the technique exposes a significant volume of the body with low radiation doses, which is often referred to as 'low-dose bath'. It has been hypothesized that IMRT may therefore increase secondary cancers, which is controversially discussed as there are to date no to little experimental (standardized) data on the incidence of secondary cancers in low-dose areas. Our group has commissioned a Micro-CT as small-animal irradiation device and, as a first step of this proposal, we now aim to establish a Monte-Carlo-based planning system to enable small animal IMRT. We will then define a fixed target volume in tumor-permissive rats, which will be irradiated either conventionally (via opposing fields) or via rotations in an intensity-modulated fashion. The primary objective is comparing induced tumor incidences in high-, low- and no-dose areas. A secondary goal is to establish overall and cancer-free survival rates. The project displays the first standardized comparative assessment of cancer incidences after conventional and modulated radiotherapy and will provide data for a re-assessment of risks associated with the technique.