Comparison of diagnostic sensitivity of [18F]fluoroestradiol and [18F]fluorodeoxyglucose positron emission tomography/computed tomography for breast cancer recurrence in patients with a history of estrogen receptor-positive primary breast cancer

Background To compare the diagnostic sensitivity of [ 18 F]fluoroestradiol ([ 18 F]FES) and [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) positron emission tomography/computed tomography (PET/CT) for breast cancer recurrence in patients with estrogen receptor (ER)-positive primary breast cancer. Methods Our database of consecutive patients enrolled in a previous prospective cohort study to assess [ 18 F]FES PET/CT was reviewed to identify eligible patients who had ER-positive primary breast cancer with suspected first recurrence at presentation and who underwent [ 18 F]FDG PET/CT. The sensitivity of qualitative [ 18 F]FES and [ 18 F]FDG PET/CT interpretations was assessed, comparing them with histological diagnoses. Results Of the 46 enrolled patients, 45 were confirmed as having recurrent breast cancer, while one was diagnosed with chronic granulomatous inflammation. Forty (89%) patients were ER-positive, four (9%) were ER-negative, and one (2%) patient did not undergo an ER assay. The sensitivity of [ 18 F]FES PET/CT was 71.1% (32/45, 95% CI, 55.7–83.6), while that of [ 18 F]FDG PET/CT was 80.0% (36/45, 95% CI, 65.4–90.4) with a threshold of positive interpretation, and 93.3% (42/45, 95% CI, 81.7–98.6) when a threshold of equivocal was used. There was no significant difference in sensitivity between [ 18 F]FES and [ 18 F]FDG PET/CT ( P = 0.48) with a threshold of positive [ 18 F]FDG uptake, but the sensitivity of [ 18 F]FDG was significantly higher than [ 18 F]FES ( P = 0.013) with a threshold of equivocal [ 18 F]FDG uptake. One patient with a benign lesion showed negative [ 18 F]FES but positive [ 18 F]FDG uptake. Conclusions The restaging of patients who had ER-positive primary breast cancer and present with recurrent disease may include [ 18 F]FES PET/CT as an initial test when standard imaging studies are equivocal or suspicious.