Head-to-head comparison of ¹⁸F-FDG and ¹⁸F-FES PET/CT for initial staging of ER-positive breast cancer patients

Purpose: To compare the diagnostic performance of F-18-fluorodeoxyglucose (F-18-FDG) and 18F-fluoroestradiol (F-18-FES) positron emission tomography/computed tomography (PET/CT) for initial staging of estrogen receptor (ER) positive breast cancer.Methods: Twenty-eight patients with ER-positive breast cancer underwent F-18-FDG and F-18-FES PET/CT for initial staging. Diagnostic performance and concordance rates were analyzed for both radiotracers. Semiquantitative parameters of maximum standardized uptake value (SUVmax) and tumor-to-normal ratio (T/N ratio) were compared using Wilcoxon signed-rank test. Factors potentially affecting the degree of radiotracer uptake were analyzed by multi-level linear regression analysis.Results: The overall diagnostic performance of F-18-FES was comparable to F-18-FDG, except for higher specificity and NPV, with sensitivity, specificity, PPV, NPV, and accuracy of 87.56%, 100%, 100%, 35.14%, and 88.35%, respectively, for F-18-FES and 83.94%, 30.77%, 94.74%, 11.43%, and 95.37%, respectively, for F-18-FDG. Diagnostic performance of strong ER expression was better in F-18-FES but worse for( 18)F-FDG. There was a correlation of mucinous cell type and Allred score 7-8 with 18F-FES uptake, with correlation coefficients of 26.65 (19.28, 34.02), 5.90 (- 0.005, 11.81), and p-value of < 0.001, 0.05, respectively. Meanwhile, luminal B and Ki-67 were related to F-18-FDG uptake, with correlation coefficients of 2.76 (1.10, 0.20), 0.11 (0.01, 0.2), and p-value of 0.018, 0.025, respectively.Conclusion: Diagnostic performance of F-18-FES is comparable to F-18-FDG, but better for strongly ER-positive breast cancer. Combination of F-18-FES and F-18-FDG would potentially overcome the limitations of each tracer with more accurate staging.