Crook Juanita M, Potters Louis, Stock Richard G, Zelefsky Michael J
Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Canada.
Brachytherapy. 2005;4(3):186-94. doi: 10.1016/j.brachy.2005.01.002.
Although permanent seed prostate brachytherapy is associated with a low risk of serious morbidity, proctitis and prolonged irritative and obstructive urinary symptoms may occur. Data are accumulating to help establish thresholds or guidelines for minimizing toxicity, however, no uniform method of defining and calculating the dose to critical organs currently exists. We set out to examine the existing data and propose a uniform method of reporting such that results from different centers can more easily be compared.
In preparation for a panel discussion at the American Brachytherapy Society 2004 Annual Meeting, four members with expertise in prostate dosimetry and critical organ assessment performed a literature search and, supplemented with their clinical experience, formulated a proposal for defining and reporting dose in a standardized fashion to the critical organs for permanent seed prostate brachytherapy.
As previously recommended by the American Brachytherapy Society, postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy. The standard imaging for postplan assessment is the CT scan. The interval between seed implantation and postplan assessment should be reported. For rectal and urinary morbidities, the critical organs are considered to be the anterior rectum and the prostatic urethra, respectively. For erectile dysfunction, both the neurovascular bundle and penile bulb have been implicated. The rectum should be contoured on all CT scan slices where radioactive seeds are visible. Both the inner and outer walls should be contoured. The dose should be reported as RV100 and RV150, the volumes in cubic centimeters of the rectal wall receiving 100% and 150% of the prescribed dose, respectively. The urethra should be contoured as a structure on each slice where seeds can be seen. The urethra should be identified by either catheterization or fusion with transrectal ultrasound. The dose should be reported as UrD5 and UrD30, which are, respectively, the dose to 5% and 30% of the urethra in Gray. As well, a UrV150 should be reported, which is the volume in cubic centimeters of the urethra receiving 150% of the prescribed dose. No recommendations can be made at this time for reporting neurovascular bundle or penile bulb doses.
It is essential that toxicity data be collected and reported in a uniform fashion. Thus, the critical organs for toxicity must be defined and the corresponding dosimetry reported in a standard fashion such that guidelines can be established in the future based on data from a cross-section of centers.
尽管永久性前列腺籽源近距离放射治疗严重并发症的风险较低,但仍可能发生直肠炎以及长期的刺激性和梗阻性尿路症状。目前积累的数据有助于确定将毒性降至最低的阈值或指南,然而,目前尚无统一的方法来定义和计算关键器官的剂量。我们着手研究现有数据,并提出一种统一的报告方法,以便更轻松地比较不同中心的结果。
为筹备美国近距离放射治疗学会2004年年会的小组讨论,四名在前列腺剂量测定和关键器官评估方面具有专业知识的成员进行了文献检索,并结合他们的临床经验,制定了一项以标准化方式定义和报告永久性前列腺籽源近距离放射治疗关键器官剂量的提案。
正如美国近距离放射治疗学会先前推荐的那样,应在所有接受永久性前列腺近距离放射治疗的患者身上进行植入后剂量测定。计划后评估的标准成像方式是CT扫描。应报告籽源植入与计划后评估之间的时间间隔。对于直肠和尿路并发症,关键器官分别被认为是直肠前部和前列腺尿道。对于勃起功能障碍,神经血管束和阴茎球部均有影响。应在所有可见放射性籽源的CT扫描切片上勾勒出直肠轮廓。内外壁均应勾勒。剂量应报告为RV100和RV150,分别是接受规定剂量100%和150%的直肠壁体积(立方厘米)。应在每个可见籽源的切片上将尿道勾勒为一个结构。尿道应通过插管或与经直肠超声融合来识别。剂量应报告为UrD5和UrD30,分别是尿道5%和30%处的剂量(单位为戈瑞)。此外,还应报告UrV150,即接受规定剂量150%的尿道体积(立方厘米)。目前对于报告神经血管束或阴茎球部剂量尚无建议。
以统一的方式收集和报告毒性数据至关重要。因此,必须定义毒性关键器官,并以标准方式报告相应的剂量测定,以便未来能够根据多个中心的数据制定指南。