Comparison of diagnostic accuracy 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

549 Purpose: We aimed to compare the diagnostic accuracy of 18F-fluoroestradiol (18F-FES) and 18F-fluorodoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for breast cancer recurrence in patients with ER-positive primary breast cancer. Materials and Methods: We reviewed our database of the prospective cohort of consecutive patients with recurrent breast cancer. Eligible patients had ER-positive primary breast cancer, with suspected first recurrence at presentation, were enrolled in the previous prospective cohort study to assess 18F-FES PET/CT, and underwent 18F-FDG PET/CT. We assessed the diagnostic accuracy of qualitative 18F-FES and 18F-FDG PET/CT interpretation compared with histological diagnosis. Results: Of 46 enrolled patients, 45 women were confirmed as having recurrent breast cancer. But one patient was diagnosed as chronic granulomatous inflammation. Forty (89%) patients were ER-positive and four (9%) were ER-negative. One patient (2%) did not undergo ER assay. The sensitivity of 18F-FES PET/CT was 71.1% (32/45, 95% CI: 55.7-83.6). Those of 18F-FDG PET/CT were 80.0% (36/45, 95% CI: 65.4-90.4) when higher than equivocal uptake was defined as positive, and 93.3% (42/45, 95% CI: 81.7-98.6) when equivocal or higher than equivocal interpretation was considered as positive. There was no significant difference in sensitivity between of 18F-FES and 18F-FDG PET/CT (P=0.48) when higher than equivocal 18F-FDG uptake was positive, but the sensitivity of 18F-FDG was significantly higher than 18F-FES (P=0.013) when equivocal or higher uptake was positive. One patient with benign lesion showed negative 18F-FES, but higher than equivocal 18F-FDG uptake. Conclusions: Restaging of women who had ER-positive primary breast cancer and present with recurrent disease may include 18F-FES PET/CT.