title: Role of early postradiation magnetic resonance imaging scans in children with diffuse intrinsic pontine glioma.
abstract: OBJECTIVE
  To determine optimal timing of assessing postradiation radiographic response on magnetic resonance imaging (MRI) scans in pediatric patients with diffuse intrinsic pontine glioma (DIPG).
  
  
  METHODS
  Patients were treated on a prospective study at the National Cancer Institute (Protocol #06-C-0219) evaluating the effects of radiotherapy (RT). Standard RT was administered in standard fractionation over 6 weeks. Postradiation MRI scans were performed at 2 and 6-8 weeks.
  
  
  RESULTS
  Eleven patients with DIPG were evaluated. Median age was 6 years (range, 4-13 years). Patients were treated with external-beam RT to 55.8 Gy (n = 10) or 54 Gy (n = 1), with a gross tumor volume to planning target volume expansion of 1.8-2.0 cm. All patients received prescribed dose and underwent posttreatment MRI scans at 2 and 6-8 weeks. Pretreatment imaging revealed compression of fourth ventricle (n = 11); basilar artery encasement (n = 9); tumor extension outside the pons (n = 11); and tumor hemorrhage (n = 2). At the 2-week scan, basilar artery encasement improved in 7 of 9 patients, and extent of tumor was reduced in 5 of 11 patients. Fourth ventricle compression improved in 6 of 11 patients but worsened in 3 of 11 patients. Presumed necrosis was observed in 5 of 11 patients at 2 weeks and in 1 additional patient at 6-8 weeks. There was no significant difference in mean anteroposterior and transverse diameters of tumor between the 2- and 6-8-week time points. Six of 11 patients had increasing ventricular size, with no evidence of obstruction.
  
  
  CONCLUSIONS
  There is no significant difference in tumor size of DIPG patients who have received standard RT when measured at 2 weeks vs. 6-8 weeks after RT. The majority of patients had the largest change in tumor size at the 2-week post-RT scan, with evolving changes documented on the 6-8-week scan. Six of 11 patients had progressive ventriculomegaly without obstruction, suggestive of communicating hydrocephalus. To the best of our knowledge, this is the first documentation of this phenomenon in this cohort of patients.
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Christine
authors.initials: C
authors.lastname: Ko
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD. Electronic address: kaushala@mail.nih.gov.
authors.forename: Aradhana
authors.initials: A
authors.lastname: Kaushal
authors.affiliation: Radiology and Imaging Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Dima A
authors.initials: DA
authors.lastname: Hammoud
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Emilie A
authors.initials: EA
authors.lastname: Steffen-Smith
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Robyn
authors.initials: R
authors.lastname: Bent
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Deborah
authors.initials: D
authors.lastname: Citrin
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Kevin
authors.initials: K
authors.lastname: Camphausen
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Warren
mesh_terms: D000293:Adolescent; D001488:Basilar Artery / Q000473:pathology; D020295:Brain Stem Neoplasms / Q000150:complications / Q000473:pathology* / Q000532:radiotherapy*; D002543:Cerebral Hemorrhage / Q000175:diagnosis; D002648:Child; D002675:Child, Preschool; D003251:Constriction, Pathologic / Q000473:pathology / Q000532:radiotherapy; D019583:Dose Fractionation, Radiation; D005260:Female; D020546:Fourth Ventricle / Q000473:pathology; D006801:Humans; D006849:Hydrocephalus / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D058958:Organs at Risk; D011149:Pons / Q000473:pathology*; D011446:Prospective Studies; D013997:Time Factors; D047368:Tumor Burden / Q000528:radiation effects