Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN 38120, USA.
Radiother Oncol. 2010 Aug;96(2):216-22. doi: 10.1016/j.radonc.2010.02.031. Epub 2010 Mar 27.
Quantify the dosimetric effect of inter- and intrafractional motion on intensity-modulated radiation therapy (IMRT) and three-dimensional (3D) planning via changes in the generalized equivalent uniform dose (gEUD), predicted tumor control probability (TCP) and normal tissue complication probability (NTCP) for pediatric ependymoma.
Twenty patients treated between 1998 and 2002 with a 3D plan (CTV = 1 cm, PTV = 5 mm) were selected. Two IMRT plans were created for the 1 cm CTV (PTV = 5 mm and PTV = 0 mm), and a third IMRT plan for a 5 mm CTV (PTV = 0 mm). Direct simulation with inter- and intrafractional motion was performed for 3D and IMRT plans based on daily pre and post-treatment cone beam CT information obtained from 20 well-matched patients (age, supine/prone, use of GA) on a localization protocol. Calculated TCP, NTCP, Conformity Index (CI), and predictive IQ were compared.
IMRT improved the calculated TCP by 2.8+/-2.8 vs. 3D (p<0.001). Inter- and intrafractional motion results in a TCP loss of 0.4+/-0.7 (p=0.02) and 0.0+/-0.1 (p=0.14) for the IMRT plan with PTV = 0 mm. Mean NTCP for 3D and IMRT with PTV = 5 mm, PTV = 0 mm, and CTV = 5 mm for the cochlea was: 66.6, 29.4, 8.7. Mean NTCP change due to motion was <5%. CI was 0.70+/-0.06 for IMRT and 0.5+/-0.10 for 3D. Predictive IQ was 10.0+/-10.3 points higher for IMRT vs. 3D.
IMRT improves calculated TCP vs. 3D. Daily localization can allow for a safe reduction in the PTV margin, while maintaining target coverage; reducing the CTV margin can further reduce NTCP and may reduce future side-effects.
通过改变广义等效均匀剂量（gEUD）、预测肿瘤控制概率（TCP）和正常组织并发症概率（NTCP），量化小儿室管膜瘤调强放疗（IMRT）和三维（3D）计划中内、外分次运动的剂量学效应。
选择了 1998 年至 2002 年间接受 3D 计划（CTV = 1 cm，PTV = 5 mm）治疗的 20 例患者。为 1 cm CTV（PTV = 5 mm 和 PTV = 0 mm）创建了两个 IMRT 计划，并为 5 mm CTV（PTV = 0 mm）创建了第三个 IMRT 计划。根据 20 名匹配良好的患者（年龄、仰卧/俯卧、使用 GA）的定位方案，每天从治疗前和治疗后锥形束 CT 信息中进行 3D 和 IMRT 计划的直接模拟。比较计算出的 TCP、NTCP、适形指数（CI）和预测 IQ。
IMRT 提高了计算出的 TCP，从 3D 计划的 2.8+/-2.8 提高到 2.8+/-2.8（p<0.001）。内、外分次运动导致 IMRT 计划中 PTV = 0 mm 的 TCP 损失为 0.4+/-0.7（p=0.02）和 0.0+/-0.1（p=0.14）。3D 计划的 PTV = 5 mm、PTV = 0 mm 和 CTV = 5 mm 时，耳蜗的平均 NTCP 为 66.6、29.4、8.7。由于运动导致的平均 NTCP 变化<5%。IMRT 的 CI 为 0.70+/-0.06，3D 为 0.5+/-0.10。IMRT 比 3D 预测 IQ 高 10.0+/-10.3 分。
IMRT 提高了计算出的 TCP 与 3D 相比。每日定位可安全降低 PTV 边界，同时保持靶区覆盖；降低 CTV 边界可进一步降低 NTCP，并可能减少未来的副作用。
