Quantitative imaging of estrogen receptor expression in breast cancer with PET and 18F-fluoroestradiol.
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.
Peterson
Lanell M
LM
Department of Radiology, University of Washington/Seattle Cancer Care Alliance, Seattle, Washington 98109, USA.
Mankoff
David A
DA
Lawton
Thomas
T
Yagle
Kevin
K
Schubert
Erin K
EK
Stekhova
Svetlana
S
Gown
Allen
A
Link
Jeanne M
JM
Tewson
Timothy
T
Krohn
Kenneth A
KA
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
D014408:Biomarkers, Tumor; D019275:Radiopharmaceuticals; D011960:Receptors, Estrogen; D004958:Estradiol; C043436:16-fluoroestradiol