Wang Kung-Liahng, Yang Yuh-Cheng, Chao K S Clifford, Wu Meng-Hao, Tai Hung-Chi, Chen Tze-Chien, Huang Ming-Chao, Chen Jen-Ruei, Su Tsung-Hsien, Chen Yu-Jen
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
Int J Radiat Oncol Biol Phys. 2007 Oct 1;69(2):498-503. doi: 10.1016/j.ijrobp.2007.03.038.
Point A, used for dose specification for intracavitary brachytherapy for cervical cancer, is the point at which the uterine artery and ureter cross. This study assessed compatibility of commonly used traditional point A (TPA) and actual anatomic point A (APA).
We visualized and placed radiopaque clips at the APA during pelvic and paraaortic lymphadenectomy in 11 patients with cervical carcinoma. Orthogonal and oblique radiographs were obtained after insertion of brachytherapy applicators. We measured the distance between the TPA and APA and estimated the brachytherapy dose to each of the two points.
A total of 64 brachytherapy treatments were performed. The mean distances between the TPA and APA were 5.2 +/- 1.0 cm on the right and 5.4 +/- 1.1 cm on the left. The estimated brachytherapy doses delivered to the APA as a percentage of the presumed 500-cGy fraction size to the TPA were 35.2% (176.6 +/- 59.0 cGy) on the right and 30.0% (150.2 +/- 42.9 cGy) on the left. The marked discrepancy in the position of the two points was not related to individual kinetic variations during brachytherapy treatment, tumor size, or bladder filling.
The conventional TPA does not provide an accurate estimate of the APA determined during lymphadenectomy, indicating a need to reevaluate the current practice for determining the brachytherapy prescription for cervical cancer. (ClinicalTrials.gov Identifier, NCT00319462).
用于宫颈癌腔内近距离放射治疗剂量设定的A点，是子宫动脉与输尿管交叉处。本研究评估了常用的传统A点（TPA）与实际解剖学A点（APA）的兼容性。
我们在11例宫颈癌患者的盆腔及腹主动脉旁淋巴结清扫术中，在APA处可视化并放置了不透X线的夹子。插入近距离放射治疗施源器后获得正交和斜位X线片。我们测量了TPA与APA之间的距离，并估计了两点各自的近距离放射治疗剂量。
共进行了64次近距离放射治疗。TPA与APA之间的平均距离右侧为5.2±1.0 cm，左侧为5.4±1.1 cm。以假定给予TPA的500 cGy分次剂量为参照，估计给予APA的近距离放射治疗剂量右侧为35.2%（176.6±59.0 cGy），左侧为30.0%（150.2±42.9 cGy）。两点位置的明显差异与近距离放射治疗期间的个体动力学变化、肿瘤大小或膀胱充盈无关。
传统的TPA不能准确估计淋巴结清扫术中确定的APA，这表明需要重新评估目前确定宫颈癌近距离放射治疗处方的做法。（ClinicalTrials.gov标识符，NCT00319462）
