There are some data that suggest that in ER+ breast cancers, 18F-fluoroestradiol (FES) PET/CT may detect more metastatic lesions (including bone) than 18F-FDG PET/CT.26 A meta-analysis of four studies that focused on metastatic lesions including bone, showed an overall sensitivity of 78% and specificity of 98% compared to immunohistochemical ER analysis.27 This evidence concerns the gene ESR1 and breast cancer.