title: Quantitative imaging of estrogen receptor expression in breast cancer with PET and 18F-fluoroestradiol.
abstract: The PET compound (18)F-fluoroestradiol ((18)F-FES) has been developed and tested as an agent for the imaging of estrogen receptor (ER) expression in vivo. (18)F-FES uptake has been shown to correlate with ER expression assayed in vitro by radioligand binding; however, immunohistochemistry (IHC) rather than radioligand binding is used most often to measure ER expression in clinical practice. We therefore compared (18)F-FES uptake with ER expression assayed in vitro by IHC with both qualitative and semiquantitative measures.
  
  
  METHODS
  Seventeen patients with primary or metastatic breast cancer were studied with dynamic (18)F-FES PET; cancer tissue samples, collected close to the time of imaging, were assayed for ER expression by IHC. For each tumor, partial-volume-corrected measures of (18)F-FES uptake were compared with ER expression measured by 3 different ER scoring methods: qualitative scoring (0-3+), the Allred score (0-10), and a computerized IHC index.
  
  
  RESULTS
  There was excellent agreement (r = 0.99) between observers using IHC as well as the different methods of measuring ER content (P < 0.001). ER-negative tumors had (18)F-FES partial-volume-corrected standardized uptake values of less than 1.0, whereas ER-positive tumors had values above 1.1. Correlation coefficients for the different measures of ER content and the different measures of (18)F-FES uptake ranged from 0.57 to 0.73, with the best correlation being between the computerized IHC index and (18)F-FES partial-volume-corrected standardized uptake values.
  
  
  CONCLUSIONS
  Our results showed good agreement between (18)F-FES PET and ER expression measured by IHC. (18)F-FES imaging may be a useful tool for aiding in the assessment of ER status, especially in patients with multiple tumors or for tumors that are difficult to biopsy.
authors.affiliation: Department of Radiology, University of Washington/Seattle Cancer Care Alliance, Seattle, Washington 98109, USA.
authors.forename: Lanell M
authors.initials: LM
authors.lastname: Peterson
authors.forename: David A
authors.initials: DA
authors.lastname: Mankoff
authors.forename: Thomas
authors.initials: T
authors.lastname: Lawton
authors.forename: Kevin
authors.initials: K
authors.lastname: Yagle
authors.forename: Erin K
authors.initials: EK
authors.lastname: Schubert
authors.forename: Svetlana
authors.initials: S
authors.lastname: Stekhova
authors.forename: Allen
authors.initials: A
authors.lastname: Gown
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Link
authors.forename: Timothy
authors.initials: T
authors.lastname: Tewson
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Krohn
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011960:Receptors, Estrogen / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D019275:Radiopharmaceuticals; D011960:Receptors, Estrogen; D004958:Estradiol; C043436:16-fluoroestradiol