Despite the theoretically lower sensitivity of [18F]FES PET/CT for breast cancer recurrence, positive [18F]FES uptake could replace histological diagnosis of recurrent breast cancer and positive ER expression [31] and could lead to a reduction in the number of false-positive diagnoses and biopsies compared with [18F]FDG PET/CT [40]. This evidence concerns the gene ESR1 and breast carcinoma.