title: Risk factors for brain injury after carbon ion radiotherapy for skull base tumors.
abstract: OBJECTIVE
  This study aimed to determine the risk factors for radiation-induced brain injury (RIBI) after carbon ion radiotherapy (CIRT) for treating skull base tumors.
  
  
  METHODS
  Between April 1997 and January 2009, CIRT at a total dose of 48.0-60.8Gy equivalent (GyE) was administered in 16 fractions to 47 patients with skull base tumors. Of these patients, 39 who were followed up with magnetic resonance imaging (MRI) for more than 24months were analyzed. RIBI was assessed according to the MRI findings based on the Late Effects of Normal Tissue-Subjective, Objective, Management, Analytic criteria; clinical symptoms were assessed according to the Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer tables. The correlations of clinical and dosimetric parameters with incidence of ⩾grade 2 RIBI were retrospectively analyzed.
  
  
  RESULTS
  The median follow-up period was 67months. The 5-year actuarial likelihoods of ⩾grade 2 RIBI and ⩾grade 2 clinical symptoms were 24.5% and 7.0%, respectively. Multivariate analysis demonstrated that the brain volume receiving more than 50GyE (V50) was a significant risk factor for the development of ⩾grade 2 RIBI (p=0.004).
  
  
  CONCLUSIONS
  V50 was a significant risk factor for ⩾grade 2 RIBI after CIRT using a 16-fraction regimen.
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan. Electronic address: koto@nirs.go.jp.
authors: Masashi
authors: M
authors: Koto
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Azusa
authors: A
authors: Hasegawa
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Ryo
authors: R
authors: Takagi
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Akira
authors: A
authors: Fujikawa
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Takamichi
authors: T
authors: Morikawa
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Riwa
authors: R
authors: Kishimoto
authors: Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
authors: Keiichi
authors: K
authors: Jingu
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Hirohiko
authors: H
authors: Tsujii
authors: Research Center for Charged Particle Therapy Hospital, National Institute of Radiological Sciences, Chiba, Japan.
authors: Tadashi
authors: T
authors: Kamada
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000528:radiation effects; D001930:Brain Injuries / Q000209:etiology*; D005260:Female; D063193:Heavy Ion Radiotherapy / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012307:Risk Factors; D019291:Skull Base / Q000528:radiation effects; D019292:Skull Base Neoplasms / Q000532:radiotherapy*; D055815:Young Adult
keywords: Brain injury; Carbon ion radiotherapy; Dose–volume histogram; Skull base tumor