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Hippocampal dosimetry predicts neurocognitive function impairment after fractionated stereotactic radiotherapy for benign or low-grade adult brain tumors.
MedLine Citation:
PMID:  23312272     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
PURPOSE: To prospectively evaluate the association between hippocampal dose and long-term neurocognitive function (NCF) impairment for benign or low-grade adult brain tumors treated with fractionated stereotactic radiotherapy (FSRT).
METHODS AND MATERIALS: Adult patients with benign or low-grade adult brain tumors were treated with FSRT per institutional practice. No attempt was made to spare the hippocampus. NCF testing was conducted at baseline and 18 months follow-up, on a prospective clinical trial. Regression-based standardized z scores were calculated by using similar healthy control individuals evaluated at the same test-retest interval. NCF impairment was defined as a z score ≤-1.5. After delineation of the bilateral hippocampi according to the Radiation Therapy Oncology Group contouring atlas, dose-volume histograms were generated for the left and right hippocampi and for the composite pair. Biologically equivalent doses in 2-Gy fractions (EQD(2)) assuming an α/β ratio of 2 Gy were computed. Fisher's exact test and binary logistic regression were used for univariate and multivariate analyses, respectively. Dose-response data were fit to a nonlinear model.
RESULTS: Of 29 patients enrolled in this trial, 18 completed both baseline and 18-month NCF testing. An EQD(2) to 40% of the bilateral hippocampi >7.3 Gy was associated with impairment in Wechsler Memory Scale-III Word List (WMS-WL) delayed recall (odds ratio [OR] 19.3; p = 0.043). The association between WMS-WL delayed recall and EQD(2) to 100% of the bilateral hippocampi >0.0 Gy trended to significance (OR 14.8; p = 0.068).
CONCLUSION: EQD(2) to 40% of the bilateral hippocampi greater than 7.3 Gy is associated with long-term impairment in list-learning delayed recall after FSRT for benign or low-grade adult brain tumors. Given that modern intensity-modulated radiotherapy techniques can reduce the dose to the bilateral hippocampi below this dosimetric threshold, patients should be enrolled in ongoing prospective trials of hippocampal sparing during cranial irradiation to confirm these preliminary results.
Authors:
Vinai Gondi; Bruce P Hermann; Minesh P Mehta; Wolfgang A Tomé
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  International journal of radiation oncology, biology, physics     Volume:  85     ISSN:  1879-355X     ISO Abbreviation:  Int. J. Radiat. Oncol. Biol. Phys.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7603616     Medline TA:  Int J Radiat Oncol Biol Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  348-54     Citation Subset:  IM    
Copyright Information:
Copyright © 2013. Published by Elsevier Inc.
Affiliation:
Department of Human Oncology, University of Wisconsin, Madison, WI.
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