title: Growth hormone secretion after conformal radiation therapy in pediatric patients with localized brain tumors.
abstract: OBJECTIVE
  Growth hormone deficiency (GHD) after radiation therapy negatively affects growth and development and quality of life in children with brain tumors.
  
  
  METHODS
  Between 1997 and 2008, 192 pediatric patients with localized primary brain tumors (ependymoma, n = 88; low-grade glioma, n = 51; craniopharyngioma, n = 28; high-grade glioma, n = 23; and other tumor types, n = 2) underwent provocative testing of GH secretion by using the secretogogues arginine and L-dopa before and after (6, 12, 36, and 60 months) conformal radiation therapy (CRT). A total of 664 arginine/l-dopa test procedures were performed.
  
  
  RESULTS
  Baseline testing revealed preirradiation GHD in 22.9% of tested patients. On the basis of data from 118 patients, peak GH was modeled as an exponential function of time after CRT and mean radiation dose to the hypothalamus. The average patient was predicted to develop GHD with the following combinations of the time after CRT and mean dose to the hypothalamus: 12 months and more than 60 Gy; 36 months and 25 to 30 Gy; and 60 months and 15 to 20 Gy. A cumulative dose of 16.1 Gy to the hypothalamus would be considered the mean radiation dose required to achieve a 50% risk of GHD at 5 years (TD(50/5)).
  
  
  CONCLUSIONS
  GH secretion after CRT can be predicted on the basis of dose and time after irradiation in pediatric patients with localized brain tumors. These findings provide an objective radiation dose constraint for the hypothalamus.
authors: St Jude Children’s Research Hospital, Memphis, TN 38015-3678, USA. thomas.merchant@stjude.org
authors: Thomas E
authors: TE
authors: Merchant
authors: Susan R
authors: SR
authors: Rose
authors: Christina
authors: C
authors: Bosley
authors: Shengjie
authors: S
authors: Wu
authors: Xiaoping
authors: X
authors: Xiong
authors: Robert H
authors: RH
authors: Lustig
mesh_terms: D001932:Brain Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D002648:Child; D016371:Cranial Irradiation / Q000009:adverse effects*; D019382:Human Growth Hormone / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D007031:Hypothalamus / Q000528:radiation effects; D008137:Longitudinal Studies; D011336:Probability; D020266:Radiotherapy, Conformal / Q000009:adverse effects*
chemical_list: D019382:Human Growth Hormone