title: Response of rat intracranial 9L gliosarcoma to microbeam radiation therapy.
abstract: 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.
authors.affiliation: Medical Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: F Avraham
authors.initials: FA
authors.lastname: Dilmanian
authors.forename: Terry M
authors.initials: TM
authors.lastname: Button
authors.forename: Géraldine
authors.initials: G
authors.lastname: Le Duc
authors.forename: Nan
authors.initials: N
authors.lastname: Zhong
authors.forename: Louis A
authors.initials: LA
authors.lastname: Peña
authors.forename: Jennifer A L
authors.initials: JA
authors.lastname: Smith
authors.forename: Steve R
authors.initials: SR
authors.lastname: Martinez
authors.forename: Tigran
authors.initials: T
authors.lastname: Bacarian
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tammam
authors.forename: Baorui
authors.initials: B
authors.lastname: Ren
authors.forename: Peter M
authors.initials: PM
authors.lastname: Farmer
authors.forename: John
authors.initials: J
authors.lastname: Kalef-Ezra
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Micca
authors.forename: Marta M
authors.initials: MM
authors.lastname: Nawrocky
authors.forename: James A
authors.initials: JA
authors.lastname: Niederer
authors.forename: F Peter
authors.initials: FP
authors.lastname: Recksiek
authors.forename: Alexander
authors.initials: A
authors.lastname: Fuchs
authors.forename: Eliot M
authors.initials: EM
authors.lastname: Rosen
mesh_terms: 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