Lyons Ciara A, King Raymond B, Osman Sarah O S, McMahon Stephen J, O'Sullivan Joe M, Hounsell Alan R, Jain Suneil, McGarry Conor K
Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, BT7 1NN, UK.
Clinical Oncology, Northern Ireland Cancer Centre, Belfast City Hospital, Belfast, UK.
Radiat Oncol. 2017 Aug 4;12(1):124. doi: 10.1186/s13014-017-0859-z.
Traditional CTV-PTV margin recipes are not generally applicable in the situation of stereotactic ablative radiotherapy (SABR) treatments of multiple target volumes with a single isocentre. In this work, we present a novel geometric method of margin derivation based on CBCT-derived anatomical data.
Twenty patients with high-risk localized prostate cancer were selected for retrospective review. Individual volumes of interest (prostate, prostate and seminal vesicles and pelvic lymph nodes) were delineated on five representative CBCTs and registered to the planning CT using two registration protocols: bone match or prostate-based soft tissue match. Margins were incrementally expanded around composite CTV structures until 95% overlap was achieved.
CTV-PTV margins of 5.2, 6.5 and 7.6 mm were required for prostate, prostate and seminal vesicles and pelvic lymph nodes respectively using a prostate matching protocol. For the prostate and seminal vesicle structures, margins calculated using our method displayed good agreement with a conventional margin recipe (within ±1.0 mm).
We have presented an alternative method of CTV-PTV margin derivation that is applicable to SABR treatments with more than one isocentric target. These results have informed an institutional trial of prostate and pelvic nodal SABR in men with high-risk localized prostate cancer.
传统的临床靶区（CTV）到计划靶区（PTV）的边界设定方法通常不适用于在单一等中心对多个靶区进行立体定向消融放疗（SABR）的情况。在本研究中，我们提出了一种基于CBCT衍生的解剖数据的新型边界推导几何方法。
选择20例高危局限性前列腺癌患者进行回顾性分析。在五幅代表性的CBCT图像上勾勒出感兴趣的个体靶区（前列腺、前列腺和精囊以及盆腔淋巴结），并使用两种配准方案将其配准到计划CT上：骨匹配或基于前列腺的软组织匹配。围绕复合CTV结构逐步扩大边界，直到达到95%的重叠率。
使用前列腺匹配方案时，前列腺、前列腺和精囊以及盆腔淋巴结的CTV-PTV边界分别需要5.2、6.5和7.6毫米。对于前列腺和精囊结构，使用我们的方法计算出的边界与传统边界设定方法显示出良好的一致性（在±1.0毫米范围内）。
我们提出了一种CTV-PTV边界推导的替代方法，该方法适用于具有多个等中心靶区的SABR治疗。这些结果为一项针对高危局限性前列腺癌男性的前列腺和盆腔淋巴结SABR的机构试验提供了依据。
