title: Improved hippocampal dose with reduced margin radiotherapy for glioblastoma multiforme.
abstract: BACKGROUND
  To dosimetrically evaluate the effect of reduced margin radiotherapy on hippocampal dose for glioblastoma multiforme (GBM) patients.
  
  
  METHODS
  GBM patients enrolled on the Radiation Therapy Oncology Group (RTOG) 0825 trial at our institution were identified. Standard RTOG 0825 expansions were 2 cm + 3-5 mm from the gross tumor volume (GTV) to the clinical tumor volume (CTV) and from the CTV to the planning tumor volume (PTV), respectively. These same patients also had reduced margin tumor volumes generated with 8 mm (GTV to CTV) + 3 mm (CTV to PTV) expansions. Individual plans were created for both standard and reduced margin structures. The dose-volume histograms were statistically compared with a paired, two-tailed Student's t-test with a significance level of p < 0.05.
  
  
  RESULTS
  A total of 16 patients were enrolled on RTOG 0825. The reduced margins resulted in statistically significant reductions in hippocampal dose at all evaluated endpoints. The hippocampal Dmax was reduced from a mean of 61.4 Gy to 56.1 Gy (8.7%), D40% was reduced from 49.9 Gy to 36.5 Gy (26.9%), D60% was reduced from 32.7 Gy to 18.7 Gy (42.9%) and the D80% was reduced from 27.3 Gy to 15.3 Gy (44%).
  
  
  CONCLUSIONS
  The use of reduced margin PTV expansions in the treatment of GBM patients results in significant reductions in hippocampal dose. Though the exact clinical benefit of this reduction is currently unclear, this study does provide support for a future prospective trial evaluating the neurocognitive benefits of reduced margin tumor volumes in the treatment of GBM patients.
authors.affiliation: Department of Radiation Oncology, Emory University, 1365 Clifton Rd, NE, Atlanta, GA 30322, USA. aali24@emory.edu.
authors.forename: Arif N
authors.initials: AN
authors.lastname: Ali
authors.forename: Tomi
authors.initials: T
authors.lastname: Ogunleye
authors.forename: Claire W
authors.initials: CW
authors.lastname: Hardy
authors.forename: Hui-Kuo
authors.initials: HK
authors.lastname: Shu
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Curran
authors.forename: Ian R
authors.initials: IR
authors.lastname: Crocker
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000628:therapy; D059248:Chemoradiotherapy; D017024:Chemotherapy, Adjuvant; D017326:Clinical Trials, Phase III as Topic; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000627:therapeutic use; D005909:Glioblastoma / Q000473:pathology / Q000532:radiotherapy* / Q000628:therapy; D006624:Hippocampus / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D058958:Organs at Risk; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D000077204:Temozolomide; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D003606:Dacarbazine; D000077204:Temozolomide