The possible role of combined (¹⁸F)-Fluoroestradiol (¹⁸F-FES) and ¹⁸F-FDG PET/CT scans in early detection of molecular heterogeneity and prognosis to hormonal treatment response in metastatic estrogen positive (ER+) breast cancer (BC) patients: A case report

F 18 fluoroestradiol (F-18 FES) is the first F-18 positron emission tomography/computed tomography (PET/CT) imaging agent indicated for the detection of estrogen receptor (ER)-positive lesions in patients with recurrent or metastatic breast cancer (BC), while the fluorodeoxyglucose F¹⁸ (¹⁸F-FDG) can estimate the glucose metabolism and plays an important role in the management of BC patients. Patient refused to change the therapy and on close follow-up scans within 1 month FDG showed a disease progression at the primary site (FDG SUVmax raised to 2.45, on further follow-up scans to 7.5), axillary lymph nodes became multiple with (SUVmax 6.58), persistent hypermetabolic bone lesion (FDG SUVmax 4.02) and on NaF scan progression of the lesion in the head of the left femur as well as reactivation of the old metastases. A single FES-negative/FDG-positive lesion may indicate appearance of early metabolic heterogeneity in metastatic BC and may play role in the prognosis and hormonal treatment response that can help to modify the treatment plan in ER+ BC patients receiving hormonal treatment.