Mavroidis Panayiotis, Ferreira Brigida Costa, Shi Chengyu, Delichas Miltiadis G, Lind Bengt K, Papanikolaou Nikos
Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University, Stockholm, Sweden.
Technol Cancer Res Treat. 2009 Feb;8(1):3-14. doi: 10.1177/153303460900800102.
The investigation of the clinical efficacy and effectiveness of Intensity Modulated Radiotherapy (IMRT) using Multileaf Collimators (MLC) and Helical Tomotherapy (HT) has been an issue of increasing interest over the past few years. In order to assess the suitability of a treatment plan, dosimetric criteria such as dose-volume histograms (DVH), maximum, minimum, mean, and standard deviation of the dose distribution are typically used. Nevertheless, the radiobiological parameters of the different tumors and normal tissues are often not taken into account. The use of the biologically effective uniform dose (D=) together with the complication-free tumor control probability (P(+)) were applied to evaluate the two radiation modalities. Two different clinical cases of brain and cranio-spinal axis cancers have been investigated by developing a linac MLC-based step-and-shoot IMRT plan and a Helical Tomotherapy plan. The treatment plans of the MLC-based IMRT were developed on the Philips treatment planning station using the Pinnacle 7.6 software release while the dedicated Tomotherapy treatment planning station was used for the HT plan. With the use of the P(+) index and the D(=) concept as the common prescription point, the different treatment plans were compared based on radiobiological measures. The tissue response probabilities were plotted against D(=) for a range of prescription doses. The applied plan evaluation method shows that in the brain cancer, the HT treatment gives slightly better results than the MLC-based IMRT in terms of optimum expected clinical outcome (P(+) of 66.1% and 63.5% for a D(=) to the PTV of 63.0 Gy and 62.0 Gy, respectively). In the cranio-spinal axis cancer, the HT plan is significantly better compared to the MLC-based IMRT plan over the clinically useful dose prescription range (P(+) of 84.1% and 28.3% for a D(=) to the PTV of 50.6 Gy and 44.0 Gy, respectively). If a higher than 5% risk for complications could be allowed, the complication-free tumor control could be increased by almost 30% compared to the initial dose prescription. In comparison to MLC based-IMRT, HT can better encompass the often large PTV while minimizing the volume of the OARs receiving high dose. A radiobiological treatment plan evaluation can provide a closer association of the delivered treatment with the clinical outcome by taking into account the dose-response relations of the irradiated tumors and normal tissues. The use of P - (D=) diagrams can complement the traditional tools of evaluation such as DVHs, in order to compare and effectively evaluate different treatment plans.
在过去几年中，使用多叶准直器（MLC）的调强放射治疗（IMRT）和螺旋断层放射治疗（HT）的临床疗效和有效性研究一直是人们日益关注的问题。为了评估治疗计划的适用性，通常会使用剂量学标准，如剂量体积直方图（DVH）、剂量分布的最大值、最小值、平均值和标准差。然而，不同肿瘤和正常组织的放射生物学参数往往没有被考虑在内。使用生物等效均匀剂量（D=）和无并发症肿瘤控制概率（P(+)）来评估这两种放疗方式。通过制定基于直线加速器MLC的步进式IMRT计划和螺旋断层放射治疗计划，对两例不同的脑癌和颅脊髓轴癌临床病例进行了研究。基于MLC的IMRT治疗计划是在飞利浦治疗计划工作站上使用Pinnacle 7.6软件版本制定的，而专用的螺旋断层放射治疗计划工作站则用于制定HT计划。以P(+)指数和D(=)概念作为共同的处方点，基于放射生物学测量比较了不同的治疗计划。针对一系列处方剂量，绘制了组织反应概率与D(=)的关系图。应用的计划评估方法表明，在脑癌中，就最佳预期临床结果而言，HT治疗比基于MLC的IMRT略好（对于PTV的D(=)为63.0 Gy和62.0 Gy时，P(+)分别为66.1%和63.5%）。在颅脊髓轴癌中，在临床有用的剂量处方范围内，HT计划明显优于基于MLC的IMRT计划（对于PTV的D(=)为50.6 Gy和44.0 Gy时，P(+)分别为84.1%和28.3%）。如果允许并发症风险高于5%，与初始剂量处方相比，无并发症肿瘤控制可提高近30%。与基于MLC的IMRT相比，HT可以更好地覆盖通常较大的PTV，同时将接受高剂量的危及器官体积最小化。放射生物学治疗计划评估可以通过考虑受照射肿瘤和正常组织的剂量反应关系，使所给予的治疗与临床结果更紧密地关联起来。使用P - (D=)图可以补充传统的评估工具，如DVH，以便比较和有效评估不同的治疗计划。
