title: (18)F-FDOPA PET for differentiating recurrent or progressive brain metastatic tumors from late or delayed radiation injury after radiation treatment.
abstract: Brain metastases are frequently treated with radiation. It is critical to distinguish recurrent or progressive brain metastases (RPBM) from late or delayed radiation injury (LDRI). The purpose of this study was to examine the diagnostic accuracy as well as the prognostic power of 6-(18)F-fluoro-l-dopa ((18)F-FDOPA) PET for differentiating RPBM from LDRI.
  
  
  METHODS
  Thirty-two patients who had 83 previously irradiated brain metastases and who underwent (18)F-FDOPA PET because of an MR imaging-based suggestion of RPBM were studied retrospectively. PET studies were analyzed semiquantitatively (lesion-to-striatum and lesion-to-normal brain tissue ratios based on both maximum and mean standardized uptake values) and visually (4-point scale). The diagnostic accuracy of PET was verified by histopathologic analysis (n = 9) or clinical follow-up (n = 74) on a lesion-by-lesion basis. Receiver operating characteristic curve analysis was used to identify the best diagnostic indices. The power of (18)F-FDOPA PET to predict disease progression was evaluated with the Kaplan-Meier and Cox regression methods.
  
  
  RESULTS
  The best overall accuracy was achieved by visual scoring, with which a score of 2 or more (lesion uptake greater than or equal to striatum uptake) resulted in a sensitivity of 81.3% and a specificity of 84.3%. Semiquantitative (18)F-FDOPA PET uptake indices based on lesion-to-normal brain tissue ratios were significantly higher for RPBM than for LDRI. Among the various predictors tested, (18)F-FDOPA PET was the strongest predictor of tumor progression (hazard ratio, 6.26; P < 0.001), and the lesion-to-normal brain tissue ratio or visual score was the best discriminator. The mean time to progression was 4.6 times longer for lesions with negative (18)F-FDOPA PET results than for lesions with positive (18)F-FDOPA PET results (76.5 vs. 16.7 mo; P < 0.001). (18)F-FDOPA PET findings tended to predict overall survival.
  
  
  CONCLUSIONS
  Metabolic imaging with (18)F-FDOPA PET was useful for differentiating RPBM from LDRI. Semiquantitative indices, particularly lesion-to-normal uptake ratios, could be used. A visual score comparing tumor (18)F-FDOPA uptake and striatum (18)F-FDOPA uptake provided the highest sensitivity and specificity and was predictive of disease progression.
authors.affiliation: Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Karlo J
authors.initials: KJ
authors.lastname: Lizarraga
authors.forename: Martin
authors.initials: M
authors.lastname: Allen-Auerbach
authors.forename: Johannes
authors.initials: J
authors.lastname: Czernin
authors.forename: Antonio A F
authors.initials: AA
authors.lastname: DeSalles
authors.forename: William H
authors.initials: WH
authors.lastname: Yong
authors.forename: Michael E
authors.initials: ME
authors.lastname: Phelps
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D003937:Diagnosis, Differential; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D018450:Disease Progression; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011832:Radiation Injuries / Q000175:diagnosis* / Q000209:etiology; D011878:Radiotherapy / Q000009:adverse effects*; D012008:Recurrence; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D005462:Fluorine Radioisotopes; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine
keywords: 18F-FDOPA PET; brain metastases; radiation injury; radiation treatment; tumor recurrence