RT Journal Article SR Electronic T1 Value of 18F-FES-PET to solve clinical dilemmas in breast cancer patients: a retrospective study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP jnumed.120.256826 DO 10.2967/jnumed.120.256826 A1 Jorianne Boers A1 Naila Loudini A1 Celina L. Brunsch A1 Sylvia A. Koza A1 Erik F.J. de Vries A1 Andor W.J.M. Glaudemans A1 Geke A.P. Hospers A1 Carolina P. Schroder YR 2021 UL http://jnm.snmjournals.org/content/early/2021/05/14/jnumed.120.256826.abstract AB Background: Breast cancer (BC) is a heterogeneous disease, in which estrogen receptor (ER) expression plays an important role in the majority of breast tumors. A clinical dilemma may arise when a metastasis biopsy to determine the ER status cannot be performed safely or when ER heterogeneity is suspected between tumor lesions. Whole-body ER imaging, such as 16α-18F-fluoro-17β-estradiol (18F-FES) positron emission tomography (PET), may have added value in these situations. However, the role of this imaging technique in routine clinical practice remains to be further determined. Therefore, we assessed the value of 18F-FES-PET by evaluating if the physician’s clinical dilemma that remained after standard workup was solved by the 18F-FES-PET scan. Methods: In this retrospective study, 18F-FES-PET scans, performed in patients with (suspected) ER+ metastatic BC with remaining clinical dilemma after standard workup, at the University Medical Center of Groningen between November 2009 and January 2019, were included. We investigated whether the physician’s clinical dilemma was solved, defined as 1) 18F-FES-PET provided a solution for the clinical dilemma, and/or 2) a treatment decision was based directly on the 18F-FES-PET. In addition, category of clinical dilemma, and rate of 18F-FES positive or negative PET scans were reported, and related to frequency of solved dilemmas. Results: One hundred 18F-FES-PET scans were performed in 83 patients. Clinical dilemma categories were: 1) inability to determine extent of (suspected) metastatic disease with standard workup (n = 52), 2) unclear ER status of the tumor (n = 31), and 3) inability to determine which primary tumor caused metastases (n = 17). Dilemmas were solved by 18F-FES-PET in 87/100 cases (87%). In 81/87 cases a treatment decision was made based directly on the 18F-FES-PET (treatment change: n = 51 cases; continuance: n = 30 cases). The frequency of solved dilemmas was not related to the clinical dilemma category (P = 0.334). However, the frequency of solved dilemmas was related to whether scans were 18F-FES positive (n = 63) or negative (n = 37; p<0.001). Conclusion: For various indications, the 18F-FES-PET scan can help to solve the vast majority of clinical dilemmas that may remain after standard workup. Therefore, the 18F-FES-PET scan has added value in BC patients presenting with a clinical dilemma.