RT Journal Article SR Electronic T1 Diagnostic accuracy and safety of 16α-[18F]fluoro-17β-estradiol positron emission tomography/computed tomography for the assessment of estrogen receptor status of recurrent or metastatic lesions in patients with breast cancer: an open label, non-randomized, phase 3 study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 487 OP 487 VO 59 IS supplement 1 A1 Chae, Sun Young A1 Ahn, Sei Hyun A1 Kim, Sung-Bae A1 Son, Byung Ho A1 Lee, Jong Won A1 Ko, Beom Seok A1 Ahn, Jin-Hee A1 Jung, Kyung Hae A1 Kim, Jeong Eun A1 Choi, Woo Jung A1 Shin, Hee Jung A1 Gong, Gyungyub A1 Lee, Suk Hyun A1 Lee, Sang Ju A1 Oh, Seung Jun A1 KIM, SEOG-YOUNG A1 Lee, Jung Bok A1 Moon, Dae Hyuk YR 2018 UL http://jnm.snmjournals.org/content/59/supplement_1/487.abstract AB 487Objectives: The standard diagnostic workup for recurrent or metastatic breast cancer includes biopsy and determination of tumor estrogen receptor (ER) status. However, biopsy procedures are not always feasible, and thus treatment is planned according to the previous pathological findings. We aimed to evaluate the diagnostic accuracy and safety of 18F-FES positron emission tomography/computed tomography (PET/CT) in assessing ER status in patients with recurrent or metastatic breast cancer.Methods: We conducted a prospective, open-label, non-randomized phase 3 study at Asan Medical Center. Study participants eligible for inclusion were patients who were scheduled to undergo core needle biopsy or surgery of the recurrent or distant metastatic breast cancer lesions within 15 days after 18F-FES PET/CT, or had already undergone core needle biopsy of those lesions within 30 days before 18F-FES PET/CT. Whole-body 18F-FES PET/CT imaging was performed 90 minutes after intravenous injection of 111-222 MBq of 18F-FES. 18F-FES uptake in recurrent or metastatic lesions was assessed qualitatively and quantitatively. 18F-FES uptake above background intensity was interpreted as 18F-FES PET/CT positive. ER status assessed by immunohistochemical testing was used as the reference standard. We planned to study 47 ER-positive and 38 ER-negative patients assuming 10% dropouts to detect a difference between the null and alternative hypotheses of agreements (H0: <0.55 vs. H1: ≥0.75 for positive agreement; H0: <0.82 vs. H1: ≥0.97 for negative agreement) with 80% power and a significance level of 2.5% using a one-sided exact binomial test. We consecutively enrolled participants until ER-positive or ER-negative population reached the planned number of patients, and then included only those patients who did not reach the target number.Results: Between November 2013 and November 2016, we recruited 93 women, of whom 90 completed the study. Five patients were excluded from the efficacy analyses for pre-specified reasons. A total of 85 patients were included for accuracy analysis, of whom 47 had ER-positive lesions (median age 55) and 38 had ER-negative lesions (median age 54). Recurrent or metastatic sites for pathological diagnosis were lymph node (n=53), lung (n=18), chest wall (n=13) and pleura (n=1). Positive and negative percent agreements of 18F-FES PET/CT for diagnosing ER status were 76.6% (95% CI, 62.0-87.7, p=0.0018) and 100% (95% CI, 90.8-100, p=0.0005), respectively. The maximum standardized uptake values of ER-positive and negative lesions were 6.34±7.04 and 1.26±0.39, respectively (p<0.0001). A positive correlation was found between maximum standardized value of 18F-FES and Allred scores of ER immuhohistochemical testing (all 85 lesions: ρ=0.83, p<0.0001; 47 ER-positive lesions: ρ=0.70, p<0.0001). 18F-FES PET/CT was well tolerated without serious adverse events.Conclusions: 18F-FES PET/CT can noninvasively assess ER-status of recurrent or metastatic breast cancer. High specificity of 18F-FES PET/CT indicates that positive 18F-FES PET/CT results can reliably rule in the diagnosis of ER-positive recurrent or metastatic breast cancer, and thus can substitute for immunohistochemical assessment of ER-status. Registration: ClinicalTrials.gov: NCT01986569.