Tornero-López Ana M, Guirado Damián
Servicio de Radiofísica y Protección Radiológica, Hospital Universitario de Gran Canaria Dr. Negrín, E-35010 Las Palmas de Gran Canaria, Spain.
Unidad de Radiofísica, Hospital Universitario San Cecilio, E-18016 Granada, Spain.
Rep Pract Oncol Radiother. 2018 Nov-Dec;23(6):562-573. doi: 10.1016/j.rpor.2018.05.007. Epub 2018 Jul 2.
The recommended radio-therapeutic treatment for cervix cancer consists of a first phase of external beam radiotherapy (EBRT) plus a second phase of brachytherapy (BT), the combined treatment being delivered within 8 weeks. In order to assess a comprehensive dosimetry of the whole treatment, it is necessary to take into account that these two phases are characterized by different spatial and temporal dosimetric distributions, which complicates the task of the summation of the two contributions, EBRT and BT. Radiobiology allows to tackle this issue pragmatically by means of the LQ model and, in fact, this is the usual tool currently in use for this matter. In this work, we describe the rationale behind the summation of the dosimetric contributions of the two phases of the treatment, EBRT and BT, for cervix cancer, as carried out with the LQ model. Besides, we address, from a radiobiological point of view, several important considerations regarding the use of the LQ model for this task. One of them is the analysis of the effect of the overall treatment time in the result of the global treatment. Another important question considered is related to the fact that the capacity of LQ to predict the treatment outcomes is deteriorated when the dose per fraction of the radiotherapic scheme exceeds 6-10 Gy, which is a typical brachytherapy fractionation. Finally, we analyze the influence of the uncertainty and the variability of the main parameters utilized in the LQ model formulation in the assessment of the global dosimetry.
子宫颈癌推荐的放射治疗方案包括第一阶段的外照射放疗（EBRT）加第二阶段的近距离放疗（BT），联合治疗需在8周内完成。为了评估整个治疗的综合剂量测定，有必要考虑到这两个阶段具有不同的空间和时间剂量分布特征，这使得将EBRT和BT这两种剂量贡献相加的任务变得复杂。放射生物学允许通过线性二次模型（LQ模型）切实解决这个问题，事实上，这是目前处理此事常用的工具。在这项工作中，我们描述了使用LQ模型对子宫颈癌治疗的两个阶段（EBRT和BT）的剂量贡献进行相加背后的基本原理。此外，我们从放射生物学的角度探讨了关于使用LQ模型执行此任务的几个重要考虑因素。其中之一是分析总治疗时间对整体治疗结果的影响。另一个考虑的重要问题是，当放射治疗方案的分次剂量超过6 - 10 Gy（这是典型的近距离放疗分次剂量）时，LQ预测治疗结果的能力会下降。最后，我们分析了LQ模型公式中使用的主要参数的不确定性和变异性在整体剂量测定评估中的影响。
