Comparison of outcomes between overlapping structure-based and non-overlapping structure-based optimization for simultaneous integrated boost IMRT for malignant gliomas.
BACKGROUND
Intensity-modulated radiotherapy (IMRT) can deliver different doses to two target volumes with high conformity. The purpose of the present study was to compare outcomes provided by two different optimization methods, overlapping structure-based and non-overlapping structure-based methods, for simultaneous integrated boost (SIB)-IMRT for malignant gliomas.


METHODS
Treatment plans for three glioblastomas and one anaplastic astrocytoma were analyzed in the present study. The planning protocol was to deliver 70 Gy/28 fractions (fr) to the gross tumor volume (GTV) and 56 Gy/28 fr to the surrounding edema. Two different optimization methods were tested for optimizing dose distribution to the GTVand the surrounding edema. One method was the "including method", an overlapping structure-based (GTV and the clinical target volume [CTV]) optimization method. The other method was the "annulus method", a non-overlapping structure-based (GTV and the subtracted volume) optimization method. Dosimetric indexes derived from dose-volume histograms (DVHs) were used for the analysis.


RESULTS
There was no significant difference between the two methods in the mean doses of the target volumes and the doses delivered to the 5% or 95% target volumes (D05 or D95). The mean dose to the brain by the including method was significantly higher than that delivered by the annulus method (P = 0.0001). The D05 of the brain showed no significant difference between the two methods.


CONCLUSIONS
The two optimization methods provided comparable dose distributions within the target volumes and normal brain.
Suzuki
Minoru
M
Department of Radiology, Kinki University School of Medicine, Osaka, Japan. msuzuki@rri.kyoto-u.ac.jp
Nakamatsu
Kiyoshi
K
Kanamori
Shuichi
S
Okajima
Kaoru
K
Okumura
Masahiko
M
Nishimura
Yasumasa
Y
D001932:Brain Neoplasms / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005909:Glioblastoma / Q000532:radiotherapy*; D006801:Humans; D011874:Radiometry; D011878:Radiotherapy / Q000379:methods; D016896:Treatment Outcome