title: Effect of cerebellum radiation dosimetry on cognitive outcomes in children with infratentorial ependymoma.
abstract: OBJECTIVE
  Cognitive decline is a recognized effect of radiation therapy (RT) in children treated for brain tumors. The importance of the cerebellum and its contribution to cognition have been recognized; however, the effect of RT on cerebellum-linked neurocognitive deficits has yet to be explored.
  
  
  METHODS
  Seventy-six children (39 males) at a median 3.3 years of age (range, 1-17 years old) were irradiated for infratentorial ependymoma from 1997 to 2008. The total prescribed dose was 54 to 59.4 Gy administered to the postoperative tumor bed with 5- or 10-mm clinical target volume margin. Age-appropriate cognitive and academic testing was performed prior to the start of RT and was then repeated at 6 months and annually throughout 5 years. The anterior and posterior cerebellum and other normal brain volumes were contoured on postcontrast, T1-weighted postoperative magnetic resonance images registered to treatment planning computed tomography images. Mean doses were calculated and used with time after RT and other clinical covariates to model their effect on neurocognitive test scores.
  
  
  RESULTS
  Considering only the statistically significant rates in longitudinal changes for test scores and models that included mean dose, there was a correlation between mean infratentorial dose and intelligence quotient (IQ; -0.190 patients/Gy/year; P=.001), math (-0.164 patients/Gy/year; P=.010), reading (-0.137 patients/Gy/year; P=.011), and spelling scores (-0.147 patients/Gy/year; P=.012), where Gy was measured as the difference between the mean dose received by an individual patient and the mean dose received by the patient group. There was a correlation between mean anterior cerebellum dose and IQ scores (-0.116 patients/Gy/year; P=.042) and mean posterior cerebellum dose and IQ (-0.150 patients/Gy/year; P=.002), math (-0.120 patients/Gy/year; P=.023), reading (-0.111 patients/Gy/year; P=.012), and spelling (-0.117 patients/Gy/year; P=.015) scores.
  
  
  CONCLUSIONS
  Sparing portions of the cerebellum should be considered in RT planning for children with infratentorial ependymoma because of the potential impact of radiation dose on cognitive function.
authors.affiliation: Division of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee. Electronic address: thomas.merchant@stjude.org.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Merchant
authors.affiliation: Division of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Shelly
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Xiong
authors.affiliation: Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Shengjie
authors.initials: S
authors.lastname: Wu
authors.affiliation: Department of Psychology, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Heather
authors.initials: H
authors.lastname: Conklin
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002531:Cerebellum / Q000528:radiation effects*; D002648:Child; D002675:Child, Preschool; D003072:Cognition Disorders / Q000209:etiology*; D004806:Ependymoma / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D007223:Infant; D015192:Infratentorial Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D007360:Intelligence / Q000528:radiation effects*; D008297:Male; D008433:Mathematics; D058958:Organs at Risk / Q000528:radiation effects*; D011829:Radiation Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D011932:Reading; D047368:Tumor Burden