title: Dosimetric advantage of intensity-modulated radiotherapy for whole ventricles in the treatment of localized intracranial germinoma.
abstract: OBJECTIVE
  To investigate the dosimetric advantage of intensity-modulated radiotherapy (IMRT) for whole ventricles (WV) in patients with a localized intracranial germinoma receiving induction chemotherapy.
  
  
  METHODS
  Data from 12 consecutive patients with localized intracranial germinomas who received induction chemotherapy and radiotherapy were used. Four-field coplanar three-dimensional conformal radiotherapy (3D-CRT) and seven-field coplanar IMRT plans were created. In both plans, 24 Gy was prescribed in 12 fractions for the planning target volume (PTV) involving WV and tumor bed. In IMRT planning, optimization was conducted to reduce the doses to the organs at risk (OARs) as much as possible, keeping the minimum dose equivalent to that of 3D-CRT. The 3D-CRT and IMRT plans were compared in terms of the dose-volume statistics for target coverage and the OARs.
  
  
  RESULTS
  IMRT significantly increased the percentage volume of the PTV receiving 24 Gy compared with 3D-CRT (93.5% vs. 84.8%; p = 0.007), while keeping target homogeneity equivalent to 3D-CRT (p = 0.869). The absolute percentage reduction in the irradiated volume of the normal brain receiving 100%, 75%, 50%, and 25% of 24 Gy ranged from 0.7% to 16.0% in IMRT compared with 3D-CRT (p < 0.001). No significant difference was observed in the volume of the normal brain receiving 10% and 5% of 24 Gy between IMRT and 3D-CRT. Conformation number was significantly improved in IMRT (p < 0.001). For other OARs, the mean dose to the cochlea was reduced significantly in IMRT by 22.3% of 24 Gy compared with 3D-CRT (p < 0.001).
  
  
  CONCLUSIONS
  Compared with 3D-CRT, IMRT for WV improved the target coverage and reduced the irradiated volume of the normal brain in patients with intracranial germinomas receiving induction chemotherapy. IMRT for WV with induction chemotherapy could reduce the late side effects from cranial irradiation without compromising control of the tumor.
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Sakanaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000528:radiation effects; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D002552:Cerebral Ventricles / Q000528:radiation effects*; D014695:Cerebral Ventriculography / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003051:Cochlea / Q000528:radiation effects; D005260:Female; D018237:Germinoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy*; D006801:Humans; D060828:Induction Chemotherapy; D008297:Male; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D010870:Pineal Gland / Q000000981:diagnostic imaging / Q000528:radiation effects; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden; D055815:Young Adult