title: Response of intracerebral human glioblastoma xenografts to multifraction radiation exposures.
abstract: OBJECTIVE
  We investigated the effects of fractionated radiation treatments on the life spans of athymic rats bearing intracerebral brain tumors.
  
  
  METHODS
  U-251 MG or U-87 MG human glioblastoma cells were implanted into the brains of athymic rats, and the resulting tumors were irradiated once daily with various doses of ionizing radiation for 5 consecutive days or for 10 days with a 2-day break after Day 5.
  
  
  RESULTS
  Five daily doses of 1 and 1.5 Gy, and 10 doses of 0.75 and 1 Gy, cured some U-251 MG tumors. However, five daily doses of 0.5 Gy increased the survival time of animals bearing U-251 MG tumors 5 days without curing any animals of their tumors. Ten doses of 0.3 Gy given over 2 weeks extended the lifespan of the host animals 9 days without curing any animals. For U-87 MG tumors, 5 daily doses of 3 Gy produced an increased lifespan of 8 days without curing any animals, and 10 doses of 1 Gy prolonged lifespan 5.5 days without curing any animals. The differences in extension of life span between the 5- and 10-fraction protocols were minor for either tumor type.
  
  
  CONCLUSIONS
  The finding that the U-251 MG tumors are more sensitive than U-87 MG tumors, despite the fact that U-251 MG tumors contain many more hypoxic cells than U-87 MG tumors, suggests the intrinsic cellular radiosensitivities of these cell lines are more important than hypoxia in determining their in vivo radiosensitivities.
authors.affiliation: Brain Tumor Research Center, Department of Neurological Surgery, University of California San Francisco, San Francisco, CA 94143, USA.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ozawa
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Faddegon
authors.forename: Lily J
authors.initials: LJ
authors.lastname: Hu
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Bollen
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Lamborn
authors.forename: Dennis F
authors.initials: DF
authors.lastname: Deen
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D019583:Dose Fractionation, Radiation; D005909:Glioblastoma / Q000401:mortality / Q000532:radiotherapy*; D006801:Humans; D008017:Life Expectancy; D008297:Male; D011836:Radiation Tolerance / Q000502:physiology; D051381:Rats; D011923:Rats, Nude; D014183:Transplantation, Heterologous