title: Potential for improved intelligence quotient using volumetric modulated arc therapy compared with conventional 3-dimensional conformal radiation for whole-ventricular radiation in children.
abstract: OBJECTIVE
  To compare volumetric modulated arc therapy (VMAT) with 3-dimensional conformal radiation therapy (3D-CRT) in the treatment of localized intracranial germinoma. We modeled the effect of the dosimetric differences on intelligence quotient (IQ).
  
  
  METHODS
  Ten children with intracranial germinomas were used for planning. The prescription doses were 23.4 Gy to the ventricles followed by 21.6 Gy to the tumor located in the pineal region. For each child, a 3D-CRT and full arc VMAT was generated. Coverage of the target was assessed by computing a conformity index and heterogeneity index. We also generated VMAT plans with explicit temporal lobe sparing and with smaller ventricular margin expansions. Mean dose to the temporal lobe was used to estimate IQ 5 years after completion of radiation, using a patient age of 10 years.
  
  
  RESULTS
  Compared with the 3D-CRT plan, VMAT improved conformality (conformity index 1.10 vs 1.85), with slightly higher heterogeneity (heterogeneity index 1.09 vs 1.06). The averaged mean doses for left and right temporal lobes were 31.3 and 31.7 Gy, respectively, for VMAT plans and 37.7 and 37.6 Gy for 3D-CRT plans. This difference in mean temporal lobe dose resulted in an estimated IQ difference of 3.1 points at 5 years after radiation therapy. When the temporal lobes were explicitly included in the VMAT optimization, the mean temporal lobe dose was reduced 5.6-5.7 Gy, resulting in an estimated IQ difference of an additional 3 points. Reducing the ventricular margin from 1.5 cm to 0.5 cm decreased mean temporal lobe dose 11.4-13.1 Gy, corresponding to an estimated increase in IQ of 7 points.
  
  
  CONCLUSIONS
  For treatment of children with intracranial pure germinomas, VMAT compared with 3D-CRT provides increased conformality and reduces doses to normal tissue. This may result in improvements in IQ in these children.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA. xqi@mednet.ucla.edu
authors.forename: X Sharon
authors.initials: XS
authors.lastname: Qi
authors.forename: Michelle
authors.initials: M
authors.lastname: Stinauer
authors.forename: Brion
authors.initials: B
authors.lastname: Rogers
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Madden
authors.forename: Greta N
authors.initials: GN
authors.lastname: Wilkening
authors.forename: Arthur K
authors.initials: AK
authors.lastname: Liu
mesh_terms: D000367:Age Factors; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D002552:Cerebral Ventricles / Q000528:radiation effects*; D002648:Child; D018237:Germinoma / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007360:Intelligence / Q000502:physiology / Q000528:radiation effects*; D059351:Organ Sparing Treatments / Q000379:methods; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013702:Temporal Lobe / Q000528:radiation effects*; D013997:Time Factors; D047368:Tumor Burden