title: Biological implications of whole-brain radiotherapy versus stereotactic radiosurgery of multiple brain metastases.
abstract: OBJECTIVE
  The efficacy and safety of treatment with whole-brain radiotherapy (WBRT) or with stereotactic radiosurgery (SRS) for multiple brain metastases (> 10) are topics of ongoing debate. This study presents detailed dosimetric and biological information to investigate the possible clinical outcomes of these 2 modalities.
  
  
  METHODS
  Five patients with multiple brain metastases (n = 11-23) underwent SRS. Whole-brain radiotherapy plans were retrospectively designed with the same MR image set and the same structure set for each patient, using the standard opposing lateral beams and fractionation (3 Gy × 10). Physical radiation doses and biologically effective doses (BEDs) in WBRT and SRS were calculated for each lesion target and for the normal brain tissues for comparison of the 2 modalities in the context of clinical efficacy and published toxicities.
  
  
  RESULTS
  The BEDs targeted to the tumor were higher in SRS than in WBRT by factors ranging from 2.4- to 3.0- fold for the mean dose and from 3.2- to 5.3-fold for the maximum dose. In the 5 patients, mean BEDs in SRS (calculated as percentages of BEDs in WBRT) were 1.3%-34.3% for normal brain tissue, 0.7%-31.6% for the brainstem, 0.5%-5.7% for the chiasm, 0.2%-5.7% for optic nerves, and 0.6%-18.1% for the hippocampus.
  
  
  CONCLUSIONS
  The dose-volume metrics presented in this study were essential to understanding the safety and efficacy of WBRT and SRS for multiple brain metastases. Whole-brain radiotherapy results in a higher incidence of radiation-related toxicities than SRS. Even in patients with > 10 brain metastases, the normal CNS tissues receive significantly lower doses in SRS. The mean normal brain dose in SRS correlated with the total volume of the lesions rather than with the number of lesions treated.
authors.affiliation: Department of Radiation Oncology, MD Anderson Cancer Center at Cooper, and.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Xue
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Kubicek
authors.forename: Jimm
authors.initials: J
authors.lastname: Grimm
authors.forename: Tamara
authors.initials: T
authors.lastname: LaCouture
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: H Warren
authors.initials: HW
authors.lastname: Goldman
authors.forename: Ellen
authors.initials: E
authors.lastname: Yorke
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery; D001943:Breast Neoplasms / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery; D016371:Cranial Irradiation / Q000009:adverse effects / Q000379:methods; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D011832:Radiation Injuries / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011878:Radiotherapy / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012720:Severity of Illness Index
keywords: BED = biologically effective dose; DVH = dose-volume histogram; GKS = Gamma Knife surgery; IDL = isodose line; LQ = linear-quadratic; RION = radiation-induced optic neuropathy; SFED = single-fraction equivalent dose; SRS = stereotactic radiosurgery; WBRT = whole-brain radiation therapy; biologically effective dose; multiple brain metastases; oncology; radiation complication; stereotactic radiosurgery; toxicities; whole-brain radiotherapy