Shiraishi Kenshiro, Nakagawa Keiichi, Yamashita Hideomi, Nakamura Naoki, Tago Masao, Ohtomo Kuni
Department of Radiology, University of Tokyo Hospital, Japan.
Radiat Med. 2006 Jan;24(1):17-22. doi: 10.1007/BF02489984.
Intensity-modulated radiation therapy (IMRT) allows greater dose conformity to the tumor target. However, IMRT, especially static delivery, usually requires more time to deliver a dose fraction than conventional external beam radiotherapy (EBRT). The authors have been using a "two-axis dynamic arc therapy" (2A-DAT) technique for prostate cancer treatment to make a concave dose distribution to spare the rectum and bladder while working with limited time and human resources. The objectives of this study were to (1) clinically implement the 2A-DAT technique, (2) evaluate the dosimetry in comparison with IMRT, and (3) analyze the initial treatment outcome.
The 2A-DAT consists of two dynamic arc therapies (DATs) with half rotation around two isocenters each in two separate symmetrical rhombi. Treatment planning is forward and on a trial-and-error basis. Thirty-four patients received 2A-DAT with a median prescribed dose of 70 Gy.
Although inferior in dose uniformity, the 2A-DAT provided equivalent sparing of normal structures to IMRT. Daily fraction delivery time for the 34 patients ranged from 6.4 to 9.6 minutes, with an average of 7.4 minutes. Five-year survival and five-year prostate specific autigen (PSA) failure-free survival were 89.3% and 79.5%, respectively. Three patients developed grade 2 proctitis.
This technique is a possible alternative to IMRT in EBRT of prostate cancer.
调强放射治疗（IMRT）能够使肿瘤靶区获得更好的剂量适形度。然而，IMRT，尤其是静态照射，通常比传统外照射放疗（EBRT）需要更长的时间来完成一个分次剂量的照射。作者一直在使用一种“双轴动态弧形治疗”（2A-DAT）技术来治疗前列腺癌，以便在有限的时间和人力资源条件下，形成凹形剂量分布，从而保护直肠和膀胱。本研究的目的是：（1）临床应用2A-DAT技术；（2）与IMRT相比评估剂量学；（3）分析初始治疗结果。
2A-DAT由两次动态弧形治疗（DAT）组成，每次在两个独立的对称菱形中围绕两个等中心进行半周旋转。治疗计划是前瞻性的且基于反复试验。34例患者接受了2A-DAT治疗，中位处方剂量为70 Gy。
尽管在剂量均匀性方面较差，但2A-DAT对正常组织的保护效果与IMRT相当。34例患者的每日分次照射时间为6.4至9.6分钟，平均为7.4分钟。5年生存率和5年无前列腺特异性抗原（PSA）失败生存率分别为89.3%和79.5%。3例患者发生2级直肠炎。
在前列腺癌的EBRT中，该技术可能是IMRT的一种替代方法。
