Document Detail

Dosimetric effect of setup motion and target volume margin reduction in pediatric ependymoma.
MedLine Citation:
PMID:  20347495     Owner:  NLM     Status:  MEDLINE    
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 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.
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 maintaining target coverage; reducing the CTV margin can further reduce NTCP and may reduce future side-effects.
Chris Beltran; Mihir Naik; Thomas E Merchant
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-27
Journal Detail:
Title:  Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology     Volume:  96     ISSN:  1879-0887     ISO Abbreviation:  Radiother Oncol     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-07-27     Completed Date:  2010-12-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8407192     Medline TA:  Radiother Oncol     Country:  Ireland    
Other Details:
Languages:  eng     Pagination:  216-22     Citation Subset:  IM    
Copyright Information:
Copyright 2010 Elsevier Ireland Ltd. All rights reserved.
Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN 38120, USA.
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MeSH Terms
Child, Preschool
Ependymoma / radiotherapy*
Prone Position
Radiotherapy Dosage
Radiotherapy, Conformal / methods*
Radiotherapy, Intensity-Modulated / methods*
Supine Position

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