title: Serial MR imaging of intracranial metastases after radiosurgery.
abstract: OBJECTIVE
  To evaluate the spatiotemporal evolution of radiosurgical induced changes both in metastases and in normal brain tissue adjacent to the lesions by serial magnetic resonance (MR) imaging.
  
  
  METHODS
  Thirty-five intracranial metastases of different primaries were treated in 25 patients by single high-dose radiosurgery. MR images acquired before radiosurgery were available in all patients. Sixty-three follow-up MR studies were performed in these patients including T2- and contrast-enhanced T1-weighted MR images. The average follow-up time was 9 +/- 5 months (mean +/- standard deviation [SD]). Based on contrast-enhanced T1-weighted MR images, tumor response was radiologically classified in the following four groups: stable disease was assumed if the average tumor diameter after treatment did not show a tumor shrinkage of more than 50% and an increase of more than 25%, partial remission as a shrinkage of tumor size of more than 50%, a disappearance of contrast-enhancing tumor as a complete remission, and an increase of tumor diameter of more than 25% as tumor progress. Moreover, we analysed signal changes on T2-weighted images in brain parenchyma adjacent to the enhancing metastases.
  
  
  RESULTS
  The overall mean survival time was 10.5 +/- 7 months, with a 1-year actuarial survival rate of 40%. Stable disease, partial or complete remission of the metastatic tumor was observed in 22 patients (88%). Central or homogeneous loss of contrast enhancement appeared to be a good prognostic sign for stable disease or partial remission. This association was statistically significant (p < 0.05). Three patients (12%) suffered from tumor progression. In eight patients (32%) with stable disease or partial remission, signal changes on T2-weighted images were observed in tissue adjacent to the contrast enhancing lesions. A progression of the high signal on T2-weighted images was seen in seven of the eight patients between 3 and 6 months after therapy, followed by a signal regression 6-18 months after irradiation.
  
  
  CONCLUSIONS
  MR imaging is a sensitive imaging tool to evaluate tumor response as well as the presence or absence of adjacent parenchymal changes following radiosurgery. Loss of homogeneous or central contrast enhancement on Gd-enhanced MR images appeared to be a good prognostic sign for tumor response. Tumor shrinkage seems not to be dependent on time. In addition, most cases of radiation induced changes in normal brain parenchyma observed on T2-weighted images seem to be self limited.
authors.affiliation: Department of Radiology, German Cancer Research Center (dkfz), Heidelberg. H.Hawighorst@dkfz-heidelberg.de
authors.forename: H
authors.initials: H
authors.lastname: Hawighorst
authors.forename: M
authors.initials: M
authors.lastname: Essig
authors.forename: J
authors.initials: J
authors.lastname: Debus
authors.forename: M V
authors.initials: MV
authors.lastname: Knopp
authors.forename: R
authors.initials: R
authors.lastname: Engenhart-Cabilic
authors.forename: S O
authors.initials: SO
authors.lastname: Schönberg
authors.forename: G
authors.initials: G
authors.lastname: Brix
authors.forename: I
authors.initials: I
authors.lastname: Zuna
authors.forename: G
authors.initials: G
authors.lastname: van Kaick
mesh_terms: D001921:Brain / Q000473:pathology* / Q000528:radiation effects / Q000601:surgery; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy / Q000556:secondary* / Q000601:surgery; D003131:Combined Modality Therapy; D003287:Contrast Media; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011379:Prognosis; D016634:Radiosurgery; D012189:Retrospective Studies; D015996:Survival Rate
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA