Dose to the intracranial arteries in stereotactic and intensity-modulated radiotherapy for skull base tumors.
OBJECTIVE
To examine retrospectively the maximum dose to the large skull base/intracranial arteries in fractionated stereotactic radiotherapy (FSRT) and intensity-modulated radiotherapy (IMRT), because of the potential risk of perfusion disturbances.


METHODS
Overall, 56 patients with tumors adjacent to at least one major artery were analyzed. Our strategy was to perform FSRT with these criteria: 1.8 Gy per fraction, planning target volume (PTV) enclosed by the 95% isodose, maximum dose 107%. Dose limits were applied to established organs at risk, but not the vessels. If FSRT planning failed to meet any of these criteria, IMRT was planned with the same objectives.


RESULTS
In 31 patients (median PTV, 23 cm3), the FSRT plan fulfilled all criteria. No artery received a dose > or =105%. Twenty-five patients (median PTV, 39 cm3) needed IMRT planning. In 11 of 25 patients (median PTV, 85 cm3), no plan satisfying all our criteria could be calculated. Only in this group, moderately increased maximum vessel doses were observed (106-110%, n = 7, median PTV, 121 cm3). The median PTV dose gradient was 29% (significantly different from the 14 patients with satisfactory IMRT plans). Three of the four patients in this group had paranasal sinus tumors.


CONCLUSIONS
The doses to the major arteries should be calculated in IMRT planning for critical tumor locations if a dose gradient >13% within the PTV can not be avoided because the PTV is large or includes air cavities.
Nieder
Carsten
C
Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. cnied@hotmail.com
Grosu
Anca L
AL
Stark
Sybille
S
Wiedenmann
Nicole
N
Busch
Raymonde
R
Kneschaurek
Peter
P
Molls
Michael
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D002536:Cerebral Arteries / Q000528:radiation effects*; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011832:Radiation Injuries / Q000517:prevention & control*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D019292:Skull Base Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D018709:Statistics, Nonparametric