The Application of 18F-FES PET in Clinical Cancer Care

Introduction [ 18 F]fluoroestradiol (FES) can be used for the noninvasive visualization and quantification of tumor estrogen receptor (ER) expression and activity and was FDA-approved as a diagnostic agent in May 2022 for detecting ER-positive lesions in patients with recurrent or metastatic breast cancer. PET imaging was also used to detect ER-positive lesions and malignancy among patients with uterine, ovarian, and other ER-positive solid tumors. We conducted a systemic review of the studies on FES PET imaging used among patients with cancer not limited to breast cancer to better understand the application of FES PET imaging. Methods PubMed/MEDLINE and Cochrane Library databases were used to perform a comprehensive and systematic search and were updated until August 15, 2022. Two authors independently reviewed the titles and abstracts of the retrieved articles by using the search algorithm and selected the articles based on the inclusion and exclusion criteria. All statistical analyses were conducted using R statistical software. Results Forty-three studies with 2352 patients were included in the qualitative synthesis, and 23 studies with 1388 patients were included in the quantitative analysis, which estimated the FES-positive detection rate. Thirty-two studies (77%) included breast cancer patients in 43 included studies. The FES SUV mean was higher in patients with endometrial cancer (3.4–5.3) than in those with breast cancer (2.05) and uterine sarcoma (1.1–2.6). The pooled detection rates of FES PET imaging were 0.80 for breast and 0.84 for ovarian cancer patients, both similar to that of 18 F-FDG. The FES uptake threshold of 1.1 to 1.82 could detect 11.1% to 45% ER heterogeneity, but the threshold of FES uptake did not have consistent predictive ability for prognosis among patients with breast cancer, unlike uterine cancer. However, FES uptake can effectively predict and monitor treatment response, especially endocrine therapy such as estradiol, ER-blocking agents (fulvestrant and tamifoxen), and aromatase inhibitors (such as letrozole and Z-endoxifen). Conclusions [ 18 F]fluoroestradiol PET is not only a convenient and accurate diagnostic imaging tool for detecting ER-expressing lesions in patients with breast and ovarian cancer but also among patients with uterine cancer. [ 18 F]fluoroestradiol PET is a noninvasive predictive and monitoring tool for treatment response and prognosis.