Dosimetric effect of setup motion and target volume margin reduction in pediatric ependymoma

作者：Beltran Chris^*; Naik Mihir; Merchant Thomas E

来源：Radiotherapy and Oncology, 2010, 96(2): 216-222.

DOI：10.1016/j.radonc.2010.02.031

• Pediatric ependymoma
• Patient motion
• Margin reduction
• IMRT

Purpose 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
Methods and materials 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 = 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 CA) on a localization protocol Calculated TCP, NTCP, Conformity Index (CI), and predictive IQ were compared
Results 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
Conclusions IMRT improves calculated TCP vs 3D Daily localization can allow for a safe reduction in the PTV margin, while maint

• 出版日期2010-8