Lowrey Nicola, Nilsson Sanna, Moutrie Zoe, Chan Philip, Cheuk Robyn
Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.
School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
J Med Imaging Radiat Oncol. 2015 Oct;59(5):640-5. doi: 10.1111/1754-9485.12341. Epub 2015 Jul 29.
The traditional use of two-dimensional geometric prescription points in intracavitary brachytherapy planning for locally advanced cervical cancer is increasingly being replaced by three-dimensional (3D) planning. This study aimed to directly compare the two planning methods to validate that CT planning provides superior dosimetry for both tumour and organs at risk (OARs) in our department.
The CT planning data of 10 patients with locally advanced cervical cancer was audited. For each CT dataset, two new brachytherapy plans were created, comparing the dosimetry of conventional American Brachytherapy Society points and 3D-optimised volumes created for the high-risk clinical target volume (HR CTV) and OARs. Total biologically equivalent doses for these structures were calculated using the modified EQD2 formula and comparative dose-volume histogram (DVH) analysis performed.
DVH analysis revealed that for the 3D-optimised plans, the prescription aim of D90 ≥ 100% was achieved for the HR CTV in all 10 patients. However, when prescribing to point A, only 50% of the plans achieved the minimum required dose to the HR CTV. Rectal and bladder dose constraints were met for all 3D-optimised plans but exceeded in two and one of the conventional plans, respectively.
This study confirms that the regionally relevant practice of CT-based 3D-optimised planning results in improved tumour dose coverage compared with traditional points-based planning methods and also improves dose to the rectum and bladder.
在局部晚期宫颈癌腔内近距离放疗计划中，传统的二维几何处方点使用方式正日益被三维（3D）计划所取代。本研究旨在直接比较这两种计划方法，以验证在我们科室，CT计划能为肿瘤和危及器官（OARs）提供更优的剂量测定。
审核了10例局部晚期宫颈癌患者的CT计划数据。对于每个CT数据集，创建了两个新的近距离放疗计划，比较了传统美国近距离放射治疗学会点的剂量测定以及为高危临床靶区（HR CTV）和OARs创建的3D优化体积的剂量测定。使用改良的EQD2公式计算这些结构的总生物等效剂量，并进行比较剂量体积直方图（DVH）分析。
DVH分析显示，对于3D优化计划，所有10例患者的HR CTV均达到了D90≥100%的处方目标。然而，当处方到A点时，只有50%的计划达到了HR CTV所需的最低剂量。所有3D优化计划均满足直肠和膀胱剂量限制，但传统计划分别有2例和1例超出限制。
本研究证实，与传统的基于点的计划方法相比，基于CT的3D优化计划的区域相关实践可提高肿瘤剂量覆盖范围，同时也能改善直肠和膀胱的剂量。
