Heterogeneity of bone metastases as an important prognostic factor in patients affected by oestrogen receptor-positive breast cancer. The role of combined [18F]Fluoroestradiol PET/CT and [18F]Fluorodeoxyglucose PET/CT

Highlights: • Glucose metabolism using FDG and oestrogen receptor using FES was evaluated in BC patients with bone metastases, candidate to endocrine therapy. • Entity of FDG uptake was the sole predictor of progression-free survival. • Neither FDG nor FES could predict overall survival. However, the combined assessment, as FES/FDG ratio, correlated with this parameter. • These findings suggest that the combination of metabolic aggressivity and low oestrogen receptor expression are predictor of poor prognosis. To assess the prognostic role of different inter and intralesional expression (heterogeneity) of oestrogen receptor (ER) in bone metastases, as identified by the combined use of [18F]FES PET/CT and [18F]FDG PET/CT in patients with oestrogen receptor-positive (ER+) metastatic breast cancer (BC).