title: Role of adaptive radiation therapy for pediatric patients with diffuse pontine glioma.
abstract: We investigate the role of adaptive radiation therapy in pediatric patients with diffuse pontine glioma and the impact of steroid-related weight gain on treatment parameters utilizing cone-beam CT. Fifteen patients with diffuse pontine glioma were treated with three-dimensional conformal radiation therapy and enrolled on a daily localization protocol. The median age was 6 years (range: 2-13 years). Patient charts were examined to obtain the prescribed daily dose of dexamethasone and weight. The original treatment plan was recalculated based on the data obtained from the daily cone-beam CT. The changes in target and critical structure doses were calculated using gEUD. Correlations between prescribed dexamethasone, weight gain, source-to-skin distance (SSD) changes and dosimetric changes were investigated. Eleven of the 15 patients gained weight during radiation therapy, with an average gain of 2.2 kg (8.0%). The mean gEUD decreased was 0.57 Gy (range: 0.24-1.4 Gy) for the PTV, and the mean gEUD increase for critical structures was 1.14%. No strong correlations between prescribed dexamethasone doses, weight gain and dosimetric changes were found. Change in SSD vs. dose to PTV was correlated (R² = 0.51). Weight gain and changes to the external surface are apparent in these patients; however, the dosimetric changes to the target and critical structures were small and in most cases did not warrant an adaptive plan. The potential exists for a decrease in target dose in these patients; therefore, they should be monitored to assess for replanning when necessary.
authors.affiliation: Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN 38120, USA. chris.beltran@stjude.org
authors.forename: Chris
authors.initials: C
authors.lastname: Beltran
authors.forename: Saumya
authors.initials: S
authors.lastname: Sharma
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Merchant
mesh_terms: D000293:Adolescent; D001932:Brain Neoplasms / Q000532:radiotherapy*; D020295:Brain Stem Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003907:Dexamethasone / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D011874:Radiometry / Q000379:methods; D011878:Radiotherapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods
chemical_list: D003907:Dexamethasone