Intratumoral Heterogeneity of Primary Breast Cancer on 18 F-FES PET/CT and dbPET Anticipated a Heterogeneous Response...

A 59-year-old woman with cT3N3M1 invasive breast cancer (ER low positive, PgR positive, HER2 negative) underwent PET/CT and dedicated breast PET scans using 18 F-FDG and 18 F-fluoroestradiol ( 18 F-FES). While most primary tumor regions displayed low FES uptake, regions of high FES uptake were also identified. Following chemotherapy with the paclitaxel and bevacizumab, 18 F-FDG PET/CT demonstrated a favorable response, but residual disease was noted in areas with high FES uptake on the pretreatment images. This case illustrated that 18 F-FES PET can depict intratumoral heterogeneity within the primary tumor, which was strongly associated with a heterogeneous response to subsequent chemotherapy.