van de Bunt Linda, van der Heide Uulke A, Ketelaars Martijn, de Kort Gerard A P, Jürgenliemk-Schulz Ina M
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands.
Int J Radiat Oncol Biol Phys. 2006 Jan 1;64(1):189-96. doi: 10.1016/j.ijrobp.2005.04.025. Epub 2005 Jun 22.
Investigating the impact of tumor regression on the dose within cervical tumors and surrounding organs, comparing conventional, conformal, and intensity-modulated radiotherapy (IMRT) and the need for repeated treatment planning during irradiation.
Fourteen patients with cervical cancer underwent magnetic resonance (MR) imaging before treatment and once during treatment, after about 30 Gy. Target volumes and critical organs were delineated. First conventional, conformal, and IMRT plans were generated. To evaluate the impact of tumor regression, we calculated dose-volume histograms for these plans, using the delineations of the intratreatment MR images. Second conformal and IMRT plans were made based on the delineations of the intratreatment MR images. First and second plans were compared.
The average volume receiving 95% of the prescribed dose (43 Gy) by the conventional, conformal, and IMRT plans was, respectively, for the bowel 626 cc, 427 cc, and 232 cc; for the rectum 101 cc, 90 cc, and 60 cc; and for the bladder 89 cc, 70 cc, and 58 cc. The volumes of critical organs at this dose level were significantly reduced using IMRT compared with conventional and conformal planning (p < 0.02 in all cases). After having delivered about 30 Gy external beam radiation therapy, the primary gross tumor volumes decreased on average by 46% (range, 6.1-100%). The target volumes on the intratreatment MR images remained sufficiently covered by the 95% isodose. Second IMRT plans significantly diminished the treated bowel volume, if the primary gross tumor volumes decreased >30 cc.
Intensity-modulated radiation therapy is superior in sparing of critical organs compared with conventional and conformal treatment, with adequate coverage of the target volumes. Intensity-modulated radiation therapy remains superior after 30 Gy external beam radiation therapy, despite tumor regression and internal organ motion. Repeated IMRT planning can improve the sparing of the bowel and rectum in patients with substantial tumor regression.
研究肿瘤退缩对宫颈肿瘤及周围器官内剂量的影响，比较传统放疗、适形放疗和调强放疗（IMRT）以及放疗期间重复治疗计划的必要性。
14例宫颈癌患者在治疗前及治疗约30 Gy后进行了一次磁共振（MR）成像。勾画靶区体积和关键器官。首先生成传统、适形和IMRT计划。为评估肿瘤退缩的影响，我们使用治疗期间MR图像的勾画结果计算这些计划的剂量体积直方图。其次根据治疗期间MR图像的勾画结果制定适形和IMRT计划。比较第一和第二计划。
传统、适形和IMRT计划中接受95%处方剂量（43 Gy）的平均体积，肠道分别为626 cc、427 cc和232 cc；直肠分别为101 cc、90 cc和60 cc；膀胱分别为89 cc、70 cc和58 cc。与传统和适形计划相比，使用IMRT时该剂量水平下关键器官的体积显著减小（所有情况p < 0.02）。在给予约30 Gy外照射放疗后，原发大体肿瘤体积平均减少46%（范围6.1 - 100%）。治疗期间MR图像上的靶区体积仍被95%等剂量线充分覆盖。如果原发大体肿瘤体积减少>30 cc，第二次IMRT计划可显著减少治疗的肠道体积。
与传统和适形治疗相比，调强放疗在保护关键器官方面更具优势，靶区体积覆盖充分。尽管肿瘤退缩和内部器官移动，在30 Gy外照射放疗后调强放疗仍具有优势。对于肿瘤显著退缩的患者，重复IMRT计划可改善肠道和直肠的保护。
