Response of rat intracranial 9L gliosarcoma to microbeam radiation therapy.
Radiotherapeutic doses for malignant gliomas are generally palliative because greater, supposedly curative doses would impart clinically unacceptable damage to nearby vital CNS tissues. To improve radiation treatment for human gliomas, we evaluated microbeam radiation therapy, which utilizes an array of parallel, microscopically thin (<100 microm) planar beams (microbeams) of synchrotron-generated X rays. Rats with i.c. 9L gliosarcoma tumors were exposed laterally to a single microbeam, 27 pm wide and 3.8 mm high, stepwise, to produce irradiation arrays with 50, 75, or 100 microm of on-center beam spacings and 150, 250, 300, or 500 Gy of in-slice, skin-entrance, single-exposure doses. The resulting array size was 9 mm wide and 10.4 mm high (using three 3.8-mm vertical tiers); the beam's median energy was -70 keV. When all data were collated, the median survival was 70 days; no depletion of nerve cells was observed. However, when data from the highest skin-entrance dose and/or the smallest microbeam spacings were excluded, the median survival time of the subset of rats was 170 days, and no white matter necrosis was observed. Others have reported unilateral single-exposure broad-beam irradiation of i.c. 9L gliosarcomas at 22.5 Gy with a median survival of only -34 days and with severe depletion of neurons. These results suggest that the therapeutic index of unidirectional microbeams is larger than that of the broad beams and that an application for microbeam radiation therapy in treating certain malignant brain tumors may be found in the future.
Dilmanian
F Avraham
FA
Medical Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
Button
Terry M
TM
Le Duc
Géraldine
G
Zhong
Nan
N
Peña
Louis A
LA
Smith
Jennifer A L
JA
Martinez
Steve R
SR
Bacarian
Tigran
T
Tammam
Jennifer
J
Ren
Baorui
B
Farmer
Peter M
PM
Kalef-Ezra
John
J
Micca
Peggy L
PL
Nawrocky
Marta M
MM
Niederer
James A
JA
Recksiek
F Peter
FP
Fuchs
Alexander
A
Rosen
Eliot M
EM
D000818:Animals; D001932:Brain Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000532:radiotherapy*; D003198:Computer Simulation; D018316:Gliosarcoma / Q000175:diagnosis / Q000473:pathology / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D009010:Monte Carlo Method; D009368:Neoplasm Transplantation; D011874:Radiometry; D011878:Radiotherapy / Q000379:methods; D051381:Rats; D011916:Rats, Inbred F344; D016019:Survival Analysis; D014407:Tumor Cells, Cultured