Koushik Kirthi, Bilimagga Ramesh, Rao Nirmala, Janaki M G, Ponni Arul, Rajeev A G
Department of Radiotherapy, MS Ramaiah Medical College, Bangalore, India.
J Contemp Brachytherapy. 2010 Sep;2(3):93-97. doi: 10.5114/jcb.2010.16919. Epub 2010 Oct 13.
In order to know the effect of variation in position of applicators to the dose received by the tumor volume, critical organs such as rectum and bladder and the correlation of variation on the clinical outcome.
36 patients with histologically proven cervical cancer, undergoing intracavitary brachytherapy (ICBT) from October 2005 to December 2006 were the subjects of the study. Two pairs of orthogonal X-ray films were taken: one prior to loading of sources and the other after removal of sources. These patients were followed up as per the RTOG criteria.
The median duration of insertion was 25 hours with a median follow up period of 6.7 months. The translational variation of the applicator position for all patients was 3 mm and 1 mm (2 SD), respectively, in the patient's lateral and antero-posterior direction. The rotational variation was 3 and 4 degrees (2 SD) in the patient's transverse and sagittal planes. Detailed analysis of source movement showed following changes in median dose: point A: 14%, point B: 2%, point P: 1%, Rectum 1: 3.5%, Rectum 2: 4% and Bladder: 9.1%. The incidence of rectal toxicity was 6/36 (16.7%) and that of bladder was 1/36 (2.8%). When the variables were grouped to evaluate the relationship, our study showed statistically significant relationship between: R2 and rectal toxicity ( value: 0.002), point A and rectal toxicity (Pearson: 0.792), lateral displacement/anteroposterior displacement and rectal toxicity ( value: 0.012/0.003), beta angle and R2 ( value: 0.002).
The geometric relationships between the ICBT applicators and the critical structures vary during the course of low dose rate brachytherapy. Source movement does result in significant dose alterations in terms of increased rate of complications, but its impact on cure rates needs to be studied in the future.
了解施源器位置变化对肿瘤体积、直肠和膀胱等关键器官所接受剂量的影响，以及该变化与临床结果的相关性。
选取2005年10月至2006年12月期间接受腔内近距离放疗（ICBT）且经组织学证实为宫颈癌的36例患者作为研究对象。拍摄两对正交X线片：一对在源加载前，另一对在源移除后。这些患者按照RTOG标准进行随访。
插入的中位持续时间为25小时，中位随访期为6.7个月。所有患者施源器位置在患者侧方和前后方向的平移变化分别为3毫米和1毫米（2标准差）。在患者的横断面和矢状面，旋转变化分别为3度和4度（2标准差）。对源运动的详细分析显示中位剂量有以下变化：A点：14%，B点：2%，P点：1%，直肠1：3.5%，直肠2：4%，膀胱：9.1%。直肠毒性发生率为6/36（16.7%），膀胱毒性发生率为1/36（2.8%）。当对变量进行分组以评估关系时，我们的研究显示以下各项之间存在统计学显著关系：R2与直肠毒性（P值：0.002），A点与直肠毒性（Pearson相关系数：0.792），侧向位移/前后位移与直肠毒性（P值：0.012/0.003），β角与R2（P值：0.002）。
在低剂量率近距离放疗过程中，ICBT施源器与关键结构之间的几何关系会发生变化。源运动确实会导致并发症发生率增加方面的显著剂量改变，但其对治愈率的影响有待未来研究。
