title: MR imaging response of brain metastases after gamma knife stereotactic radiosurgery.
abstract: OBJECTIVE
  To characterize the magnetic resonance (MR) imaging response of brain metastases after gamma knife stereotactic radiosurgery and determine whether imaging features and tumor response rates correlate with local tumor control and survival.
  
  
  METHODS
  Serial MR examinations were performed in 48 patients (25 men, 23 women; mean age, 58 years) with 78 lesions. Pretreatment and follow-up enhancing lesion volumes and imaging features were assessed. Rates of response to stereotactic radiosurgery were calculated. Prognostic imaging features affecting local control and survival were analyzed.
  
  
  RESULTS
  Local tumor control was achieved in 66 (90%) of 73 metastases at 20 weeks after stereotactic radiosurgery; 61% maintained local control at 2 years. A homogeneous baseline enhancement pattern and initial good response rate (> 50% lesion volume reduction) predicted local control. Five metastases demonstrated a transient volume increase after treatment. The median survival time after stereotactic radiosurgery was 53 weeks and correlated with systemic disease burden and primary tumor type.
  
  
  CONCLUSIONS
  Baseline homogeneous tumor enhancement and initial good response correlate with local control. Initial lesion growth does not preclude local control and may represent radiation-related change. Recognition of these serial MR imaging findings may guide image interpretation and influence treatment in patients with stereotactic radiosurgery-treated metastases.
authors.affiliation: Department of Radiology, University of Pittsburgh Medical Center, PA 15213-2582, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Peterson
authors.forename: C C
authors.initials: CC
authors.lastname: Meltzer
authors.forename: E J
authors.initials: EJ
authors.lastname: Evanson
authors.forename: J C
authors.initials: JC
authors.lastname: Flickinger
authors.forename: D
authors.initials: D
authors.lastname: Kondziolka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology; D001932:Brain Neoplasms / Q000175:diagnosis / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D016634:Radiosurgery; D015996:Survival Rate