Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade gliomas: does IMRT increase the integral dose to normal brain?
OBJECTIVE
To determine whether intensity-modulated radiotherapy (IMRT) treatment increases the total integral dose of nontarget tissue relative to the conventional three-dimensional conformal radiotherapy (3D-CRT) technique for high-grade gliomas.


METHODS
Twenty patients treated with 3D-CRT for glioblastoma multiforme were selected for a comparative dosimetric evaluation with IMRT. Original target volumes, organs at risk (OAR), and dose-volume constraints were used for replanning with IMRT. Predicted isodose distributions, cumulative dose-volume histograms of target volumes and OAR, normal tissue integral dose, target coverage, dose conformity, and normal tissue sparing with 3D-CRT and IMRT planning were compared. Statistical analyses were performed to determine differences.


RESULTS
In all 20 patients, IMRT maintained equivalent target coverage, improved target conformity (conformity index [CI] 95% 1.52 vs. 1.38, p < 0.001), and enabled dose reductions of normal tissues, including brainstem (D(mean) by 19.8% and D(max) by 10.7%), optic chiasm (D(mean) by 25.3% and D(max) by 22.6%), right optic nerve (D(mean) by 37.3% and D(max) by 28.5%), and left optic nerve (D(mean) by 40.6% and D(max) by 36.7%), p < or = 0.01. This was achieved without increasing the total nontarget integral dose by greater than 0.5%. Overall, total integral dose was reduced by 7-10% with IMRT, p < 0.001, without significantly increasing the 0.5-5 Gy low-dose volume.


CONCLUSIONS
These results indicate that IMRT treatment for high-grade gliomas allows for improved target conformity, better critical tissue sparing, and importantly does so without increasing integral dose and the volume of normal tissue exposed to low doses of radiation.
Hermanto
Ulrich
U
Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Frija
Erik K
EK
Lii
Mingfwu J
MJ
Chang
Eric L
EL
Mahajan
Anita
A
Woo
Shiao Y
SY
D000465:Algorithms; D001921:Brain / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000532:radiotherapy*; D005909:Glioblastoma / Q000532:radiotherapy*; D006801:Humans; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies