Can Fluorine-18 Fluoroestradiol Positron Emission Tomography–Computed Tomography Demonstrate the Heterogeneity of Breast Cancer In Vivo?

AimOur study was to investigate the heterogeneity of estrogen receptor (ER) expression among tumor sites by using fluorine-18 (18F) fluoroestradiol (FES) positron-emission tomography–computed tomography (PET-CT) imaging.MethodsThirty-two breast cancer patients underwent both 18F-FES and 18F fluorodeoxyglucose (FDG) PET-CTs from June 2010 to December 2011 in our center (mean age, 53 years; range, 27-77 years). We used the maximum standardized uptake value to quantify ER expression and a cutoff value of 1.5 to dichotomize results into ER+ and ER−. The difference of heterogeneity between the initial patients and patients with recurrent or metastatic disease after treatments was assessed by using the χ2 test. Also, the 18F-FES uptake was compared with the 18F-FDG uptake by use of Spearman correlation coefficients.ResultsA total number of 237 lesions in 32 patients were detected. Among them, most lesions (64.1% [152/237]) were bone metastasis. A striking 33.4-fold difference in 18F-FES uptake was observed among different patients (maximum standardized uptake value range, 0.5 to approximately 16.7), and a 8.2-fold difference was observed among lesions within the same individual (1.0 to approximately 8.2). As for 18F-FDG uptake, the difference was 11.6-fold (1.3 to approximately 15.1) and 9.9-fold (1.4 to approximately 13.8), respectively. In 28.1% (9/32) of the patients, both 18F-FES+ and 18F-FES− metastases were present, which suggests partial discordant ER expression. After treatments, 37.5% (9/24) patients with recurrent or metastatic breast cancer showed heterogeneity, whereas no untreated patient was detected to exist discordant ER expression (χ2, 4.174; P < .05). In addition, the 18F-FES uptake showed a weak correlation with the 18F-FDG uptake (ρ = 0.248; P < .05).Conclusion18F-FES and 18F-FDG uptake varied greatly both within and among patients. 18F-FES PET-CT demonstrated a conspicuous number of patients with the heterogeneity of ER expression.