Can 18F-Fluoroestradiol Positron Emission Tomography Become a New Imaging Standard in the Estrogen Receptor-positive Breast Cancer Patient: A Prospective Comparative Study with 18F-Fluorodeoxyglucose Positron Emission Tomography?

Head-to-Head comparison of [18F]FES and [18F]FDG PET/CT in breast cancer patients: has a new era come?

PURPOSE

This review systematically compared, in a head-to-head manner, the diagnostic and prognostic performance of [18F]FDG and [18F]FES PET/CT in breast cancer (BC) patients.

METHODS

A systematic literature search was conducted in PubMed, Scopus, and Web of Science databases up to January 2025, without temporal limitations or restrictions on the number of patients in the included studies, to identify relevant articles comparing the diagnostic value of [18F]FDG and [18F]FES PET in BC patients. Selected imaging studies were analyzed using a modified version of the Critical Appraisal Skills Programme checklist dedicated to systematic reviews.

RESULTS

A total of 20 papers were evaluated. Based on the CASP analysis, the quality of the study was variable. Totally, 806 patients affected by BC underwent both [18F]FDG and [18F]FES PET. Different setting of disease were considered, such as staging/diagnostic and prognostic value. In the initial staging of disease, [18F]FES PET/CT seemed to be more accurate than [18F]FDG. In the prognostic field, [18F]FES expression was a positive factor for the better prognosis, in particular when the amount of [18F]FDG uptake was low. [18F]FES seemed to be promising as a molecular agent in patients affected by invasive lobular BC.

CONCLUSION

These findings underscore the potential of [18F]FES as a complementary imaging biomarker to [18F]FDG, advocating for further studies to standardize PET metrics and refine their combined clinical utility.

The Diagnostic Accuracy of 18F-FDG PET and 18F-FES PET for Staging Grade 1-2 Estrogen Receptor-Positive Breast Cancer

Background According to current guidelines, staging of patients with locally advanced breast cancer and local-regional recurrent breast cancer is preferably performed with PET using 2-fluorine 18-fluoro-2-deoxy-d-glucose (18F-FDG). However, 18F-FDG PET might underperform in low-grade estrogen receptor (ER)-positive breast cancer. Alternatively, 16α-18F-fluoro-17β-estradiol (18F-FES) has emerged as a powerful tracer for in vivo visualization of ER-positive lesions. Purpose To assess whether 18F-FES PET improves staging of grade 1 or 2 ER-positive breast cancer compared with 18F-FDG PET. Materials and Methods Patients with clinical stage II/III or local-regional recurrent, grade 1 or 2, ER-positive breast cancer were included between December 2018 and January 2021 in this prospective multicenter pilot study. All participants underwent an 18F-FES PET examination in addition to standard staging with conventional imaging and 18F-FDG PET. Both PET scans were independently assessed. The disease stage was determined independently based on conventional imaging and 18F-FDG PET or 18F-FES PET. Relevant lesions suspected of malignancy were verified histopathologically, after which a final stage was determined. Results A total of 41 female participants (median age, 56 years [IQR, 48-71 years]) with 44 breast tumors were included. Overall, 29 of 41 participants (71%) were correctly staged at 18F-FDG PET compared with 34 of 41 (83%) at 18F-FES PET (P = .18). Seven of 10 and nine of 10 cases of lobular breast cancer were correctly staged at 18F-FDG and 18F-FES PET, respectively (70% vs 90%; P = .38) and seven of 12 and 11 of 12 cases of grade 1 tumors, respectively (58% vs 92%; P = .06). Regional lymph nodes were incorrectly staged at 18F-FDG PET in six of 44 cases (14%), whereas all cases were correctly staged at 18F-FES PET (P = .02). Both imaging methods had a sensitivity of 100% (95% CI: 59, 100) and a specificity of 91% (95% CI: 76, 98) for the detection of metastatic disease. Conclusion In this prospective pilot study, there was no evidence of a difference in diagnostic accuracy of 18F-FES PET and 18F-FDG PET in staging patients with grade 1 or 2 ER-positive breast cancer. Clinical trial registration no. NCT03726931 Published under a CC BY 4.0 license Supplemental material is available for this article. See also the editorial by Fowler in this issue.

[18F]F-FES PET for diagnosis, staging, and endocrine therapy prediction in ER-positive breast cancer: a systematic review and meta-analysis

BACKGROUND

This meta-analysis evaluates the diagnostic and staging accuracy of [18F]F-FES PET/CT, its ability to detect estrogen receptor (ER) positivity, and its effectiveness in predicting response to endocrine therapy in ER-positive (ER+) breast cancer. A systematic search of PubMed, Embase (OVID), and Web of Science databases was conducted for studies published between 2013 and June 2024. Studies involving ER + breast cancer patients who underwent [18F]F-FES PET/CT were included. We analyzed the diagnostic accuracy, ER detection capability, and predictive ability for endocrine therapy response.

RESULTS

Out of 189 studies initially identified, 21 met the inclusion criteria. For diagnosis and staging compared to [18F]F-FDG PET (10 studies), [18F]F-FES PET/CT demonstrated a sensitivity of 0.75 (95% CI: 0.62-0.85) and a false positive rate (FPR) of 0.27 (95% CI: 0.09-0.50). For ER detection (7 studies), sensitivity was 0.86 (95% CI: 0.71-0.94) with an FPR of 0.45 (95% CI: 0.19-0.73). For predicting response to endocrine therapy (12 studies), [18F]F-FES PET/CT showed a sensitivity of 0.79 (95% CI: 0.62-0.89) and an FPR of 0.58 (95% CI: 0.42-0.72).

CONCLUSIONS

[18F]F-FES PET/CT is valuable for diagnosing and staging ER + breast cancer, assessing ER status, and predicting response to endocrine therapy. Its implementation can improve treatment planning and patient outcomes in breast cancer management.

[18F]-Fluoroestradiol (FES) brain PET in the evaluation of patients with estrogen receptor positive breast cancer and known or suspected brain metastases

OBJECTIVE

Our purpose was to describe our initial institutional experience using dedicated brain [18F]-Fluoroestradiol (FES) PET/CT or PET/MRI in the management of patients with estrogen-receptor-positive (ER+) breast cancer brain metastases (BCBM), and compare to [18F]-Fluorodeoxyglucose (FDG) PET and MRI.

MATERIALS & METHODS

Patients with biopsy-proven ER+ disease and MRI findings of suspected new, progressive, or recurrent BCBM were included in this retrospective study. Clinical and demographic data were collected. Dedicated brain FES PET/CT or PET/MRI was performed for clinical purposes. Maximum standardized uptake value (SUV) in MRI-defined target lesions and SUV ratio (SUVR, referencing normal-appearing parenchyma) were obtained. Pathology and/or clinical and MRI follow-up data were used as gold standard to classify viable neoplasm versus post-radiotherapy (RT) sequelae. Mann-Whitney tests were performed to compare subgroups.

RESULTS

Seven patients met inclusion criteria. 15/16 (94 %) lesions classified as neoplasm were FES-positive. 4/4 (100 %) lesions classified as RT sequelae were FES-negative. Median tumor FES-SUVR were higher than median RT-sequelae FES-SUVR (6.0 (2.8-9.1) versus 0.5 (0.3-0.7), p < 0.01), and similarly, median tumor FES-SUV were higher than median RT-sequelae FES-SUV (4.8 (2.8-9.1) versus 0.6 (0.3-0.8), p < 0.01). Lesion-based analysis of FDG-SUV and -SUVR demonstrated a trend for higher FDG avidity in lesions characterized as neoplasm; however, this did not reach statistical significance.

CONCLUSION

Dedicated FES brain PET represents a promising adjunct modality, noting limitations of small sample size, retrospective nature of our study, and the possibility of ER expression heterogeneity. Our findings merit future prospective clinical trials incorporating dedicated brain FES PET/CT and PET/MRI in the management of patients with ER-positive disease and BCBM.

Radiotracer Innovations in Breast Cancer Imaging: A Review of Recent Progress

This review focuses on the pivotal role of radiotracers in breast cancer imaging, emphasizing their importance in accurate detection, staging, and treatment monitoring. Radiotracers, labeled with radioactive isotopes, are integral to various nuclear imaging techniques, including positron emission tomography (PET) and positron emission mammography (PEM). The most widely used radiotracer in breast cancer imaging is 18F-fluorodeoxyglucose (18F-FDG), which highlights areas of increased glucose metabolism, a hallmark of many cancer cells. This allows for the identification of primary tumors and metastatic sites and the assessment of tumor response to therapy. In addition to 18F-FDG, this review will explore newer radiotracers targeting specific receptors, such as estrogen receptors or HER2, which offer more personalized imaging options. These tracers provide valuable insights into the molecular characteristics of tumors, aiding in tailored treatment strategies. By integrating radiotracers into breast cancer management, clinicians can enhance early disease detection, monitor therapeutic efficacy, and guide interventions, ultimately improving patient outcomes. Ongoing research aimed at developing more specific and sensitive tracers will also be highlighted, underscoring their potential to advance precision medicine in breast cancer care.

Head-to-head comparison of 18F-FDG and 18F-FES PET/CT for initial staging of ER-positive breast cancer patients

PURPOSE

To compare the diagnostic performance of 18F-fluorodeoxyglucose (18F-FDG) and 18F-fluoroestradiol (18F-FES) positron emission tomography/computed tomography (PET/CT) for initial staging of estrogen receptor (ER) positive breast cancer.

METHODS

Twenty-eight patients with ER-positive breast cancer underwent 18F-FDG and 18F-FES PET/CT for initial staging. Diagnostic performance and concordance rates were analyzed for both radiotracers. Semiquantitative parameters of maximum standardized uptake value (SUVmax) and tumor-to-normal ratio (T/N ratio) were compared using Wilcoxon signed-rank test. Factors potentially affecting the degree of radiotracer uptake were analyzed by multi-level linear regression analysis.

RESULTS

The overall diagnostic performance of 18F-FES was comparable to 18F-FDG, except for higher specificity and NPV, with sensitivity, specificity, PPV, NPV, and accuracy of 87.56%, 100%, 100%, 35.14%, and 88.35%, respectively, for 18F-FES and 83.94%, 30.77%, 94.74%, 11.43%, and 95.37%, respectively, for 18F-FDG. Diagnostic performance of strong ER expression was better in 18F-FES but worse for 18F-FDG. There was a correlation of mucinous cell type and Allred score 7-8 with 18F-FES uptake, with correlation coefficients of 26.65 (19.28, 34.02), 5.90 (- 0.005, 11.81), and p-value of < 0.001, 0.05, respectively. Meanwhile, luminal B and Ki-67 were related to 18F-FDG uptake, with correlation coefficients of 2.76 (1.10, 0.20), 0.11 (0.01, 0.2), and p-value of 0.018, 0.025, respectively.

CONCLUSION

Diagnostic performance of 18F-FES is comparable to 18F-FDG, but better for strongly ER-positive breast cancer. Combination of 18F-FES and 18F-FDG would potentially overcome the limitations of each tracer with more accurate staging.

The Application of 18F-FES PET in Clinical Cancer Care: A Systematic Review

INTRODUCTION

[18F]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 SUVmean 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 18F-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

[18F]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. [18F]fluoroestradiol PET is a noninvasive predictive and monitoring tool for treatment response and prognosis.

FDG and Non-FDG Radiopharmaceuticals for PET Imaging in Invasive Lobular Breast Carcinoma

Invasive lobular cancer (ILC) is the second most frequent histological type of breast cancer (BC) and includes a heterogeneous spectrum of diseases with unique characteristics, especially the infiltrative growth pattern and metastatic spread. [¹⁸F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) is extensively used in oncology and BC patient evaluation. Its role in ILCs is considered suboptimal due to its low FDG avidity. Therefore, ILCs could benefit from molecular imaging with non-FDG tracers that target other specific pathways, contributing to precision medicine. This narrative review aims to summarize the current literature on the use of FDG-PET/CT in ILC and to discuss future opportunities given by the development of innovative non-FDG radiotracers.

Molecular Imaging Assessment of Hormonally Sensitive Breast Cancer: An Appraisal of 2-[18F]-Fluoro-2-Deoxy-Glucose and Newer Non-2-[18F]-Fluoro-2-Deoxy-Glucose PET Tracers

Hormone-sensitive breast cancer, which demonstrates hormone receptor positivity, accounts for approximately 75% of newly diagnosed breast cancer. 2-[18F]-Fluoro-2-deoxy-glucose is the nonspecific radiotracer of glucose metabolism as opposed to specific receptor based tracers like 16α-[18F]-fluoro-17β-estradiol and [18F]-fluoro-furanyl-norprogesterone, which provide essential information about receptor status in the management of hormonally active malignancies. The complementary information provided by (a) 2-[18F]-fluoro-2-deoxy-glucose imaging for staging and prognostication along with (b) analyzing the hormonal receptor status with receptor-based PET imaging in breast cancer can optimize tumor characterization and influence patient management.

Head-to-Head Comparison between 18F-FES PET/CT and 18F-FDG PET/CT in Oestrogen Receptor-Positive Breast Cancer: A Systematic Review and Meta-Analysis

¹⁸F-FDG PET/CT is a powerful diagnostic tool in breast cancer (BC). However, it might have a reduced sensitivity in differentiated, oestrogen receptor-positive (ER+) BC. In this setting, specific molecular imaging with fluorine-oestradiol (¹⁸F-FES) PET/CT could help in overcoming these limitations; however, the literature on the diagnostic accuracy of this method is limited. We therefore planned this systematic review and meta-analysis to compare ¹⁸F-FDG and ¹⁸F-FES PET/CT in ER+ BC patients. We performed a literature search to identify all studies performing a head-to-head comparison between the two methods; we excluded review articles, preclinical studies, case reports and small case series. Finally, seven studies were identified (overall: 171 patients; range: 7–49 patients). A patients-based analysis (PBA) showed that ¹⁸F-FDG and ¹⁸F-FES PET/CT had a similar high pooled sensitivity (97% and 94%, respectively) at the lesion-based analysis (LBA), ¹⁸F-FES performed slightly better than ¹⁸F-FDG (pooled sensitivity: 95% vs. 85%, respectively). Moreover, when we considered only the studies dealing with the restaging setting (n = 3), this difference in sensitivity was even more marked (98% vs. 81%, respectively). In conclusion, both tracers feature an excellent sensitivity in ER+ BC; however, ¹⁸F-FES PET/CT could be preferred in the restaging setting.

Analyzing the Estrogen Receptor Status of Liver Metastases with [18F]-FES-PET in Patients with Breast Cancer

Background: Positron emission tomography (PET) with 16α-[¹⁸F]-fluoro-17β-estradiol ([¹⁸F]-FES) can visualize estrogen receptor (ER) expression, but it is challenging to determine the ER status of liver metastases, due to high physiological [¹⁸F]-FES uptake. We evaluated whether [¹⁸F]-FES-PET can be used to determine the ER status of liver metastases, using corresponding liver biopsies as the gold standard. Methods: Patients with metastatic breast cancer (n = 23) were included if they had undergone a [¹⁸F]-FES-PET, liver metastasis biopsy, CT-scan, and [¹⁸F]-FDG-PET. [¹⁸F]-FES-PET scans were assessed by visual and quantitative analysis, tracer uptake was correlated with ER expression measured by immunohistochemical staining and the effects of region-of-interest size and background correction were determined. Results: Visual analysis allowed ER assessment of liver metastases with 100% specificity and 18% sensitivity. Quantitative analysis improved the sensitivity. Reduction of the region-of-interest size did not further improve the results, but background correction improved ER assessment, resulting in 83% specificity and 77% sensitivity. Using separate thresholds for ER+ and ER− metastases, positive and negative predictive values of 100% and 75%, respectively, could be obtained, although 30% of metastases remained inconclusive. Conclusion: In the majority of liver metastases, ER status can be determined with [¹⁸F]-FES-PET if background correction and separate thresholds are applied.

Heterogeneity of bone metastases as an important prognostic factor in patients affected by oestrogen receptor-positive breast cancer. The role of combined [18F]Fluoroestradiol PET/CT and [18F]Fluorodeoxyglucose PET/CT

PURPOSE

To assess the prognostic role of different inter and intralesional expression (heterogeneity) of oestrogen receptor (ER) in bone metastases, as identified by the combined use of [18F]FES PET/CT and [18F]FDG PET/CT in patients with oestrogen receptor-positive (ER+) metastatic breast cancer (BC).

METHODS

We analysed patients with a new diagnosis of bone metastases who were candidates for first-line systemic endocrine therapy. Before starting therapy, patients underwent baseline [18F]FES PET/CT and [18]FDG PET/CT. Semi-quantitative evaluation of whole-body bone metabolic burden (WB-B-MB) was performed on [18F]FES and [18F]FDG PET/CT in order to evaluate disease extent, tumour metabolism and ER heterogeneity. We used time-to-event analyses (Kaplan-Meier and Cox proportional-hazards methods) to estimate progression-free (PFS) and overall survival (OS), in order to assess the independent prognostic value of [18F]FES PET/CT and [18F]FDG PET/CT, alone and in combination.

RESULTS

According to our criteria, we enrolled 49 patients. Over a median follow-up of 44.7 months, 35 patients suffered disease progression (71.4 %) and 15 died of disease (30.6 %). When the risk of disease progression was calculated by means of the Cox model, only [18F]FDG WB-B-MB was independently and directly associated to PFS (p = 0.02). On analysing the association between all prognostic parameters and survival, the Cox model showed that the only parameter associated with OS was the WB-B-MB FES/FDG ratio (p = 0.01).

CONCLUSION

The combined use of [18F]FES-PET/CT and [18F]FDG-PET/CT can identify ER heterogeneity in BC bone metastases. This heterogeneity is significantly associated with survival. Moreover, the extension of the FDG-avid component correlates with the risk of disease progression.

Critical Role of 2-[18F]-fluoro-2-deoxy-glucose in Hormonally Active Malignancies

2-[18F]-fluoro-2-deoxyglucose (FDG) is the most commonly used radiotracer and provides valuable information about glucose metabolism. With the advent of newer receptor-based tracers in the management of hormonally active malignancies, the focus has been shifted from FDG. These tracers might be more specific than FDG because they target specific hormone receptors. But because FDG is widely available, this review discusses what information still can be harnessed from this workhorse of molecular imaging. The personalized implementation of FDG imaging in undifferentiated malignancies will help in characterization of tumor and may aid in patient management.

Automated synthesis of the 16α-[18F]fluoroestradiol ([18F]FES): minimization of precursor amount and resulting benefits

The 16α-[18F]Fluoroestradiol ([18F]FES) is an established PET radiotracer for estrogen positive (ER+) breast cancer. Although the radiosynthesis is well-described, the majority of the published methods suffer from modest or irreproducible yields and time-intensive purification procedures. In view of the considerable clinical applications, development of a more efficient and faster synthesis of [18F]FES still remains a task of a significant practical importance. [18F]FES was produced by a direct nucleophilic radiofluorination of 3-O-methoxymethyl-16,17-O-sulfuryl-16-epiestriol (MMSE), followed by acidic hydrolysis using HCl/CH3CN. [18F]Fluoride retained on a QMA carb cartridge (46 mg) was eluted by solution of 1.2 mg of tetrabutylammonium tosylate (TBAOTs) in EtOH. After fluorination reaction (0.3 mg MMSE, 1 ml of CH3CN/100 °C, 5 min) [18F]FES was isolated by single-cartridge SPE purification using OASIS WAX 3cc, elution accomplished with aqueous ethanol of different concentrations. On а GE TRACERlab FX N Pro automated module [18F]FES (formulated in normal saline with 5% EtOH) was obtained in 33 ± 3% yield (n = 5, non-decay corrected) within 32 min. Reduction of precursor amount, exclusion of azeotropic drying step and simplification of purification make the suggested method readily adaptable to various automated synthesizers and offers significant cost decrease.

Whole-Body Characterization of Estrogen Receptor Status in Metastatic Breast Cancer with 16α-18F-Fluoro-17β-Estradiol Positron Emission Tomography: Meta-Analysis and Recommendations for Integration into Clinical Applications

Estrogen receptor (ER) status by immunohistochemistry (IHC) of cancer tissue is currently used to direct endocrine therapy in breast cancer. Positron emission tomography (PET) with 16α-18F-fluoro-17β-estradiol (18 F-FES) noninvasively characterizes ER ligand-binding function of breast cancer lesions. Concordance of imaging and tissue assays should be established for 18 F-FES PET to be an alternative or complement to tissue biopsy for metastatic lesions. We conducted a meta-analysis of published results comparing 18 F-FES PET and tissue assays of ER status in patients with breast cancer. PubMed and EMBASE were searched for English-language manuscripts with at least 10 patients and low overall risk of bias. Thresholds for imaging and tissue classification could differ between studies but had to be clearly stated. We used hierarchical summary receiver-operating characteristic curve models for the meta-analysis. The primary analysis included 113 nonbreast lesions from 4 studies; an expanded analysis included 327 total lesions from 11 studies. Treating IHC results as the reference standard, sensitivity was 0.78 (95% confidence region 0.65-0.88) and specificity 0.98 (0.65-1.00) for the primary analysis of nonbreast lesions. In the expanded analysis including non-IHC tissue assays and all lesion sites, sensitivity was 0.81 (0.73-0.87) and specificity 0.86 (0.68-0.94). These results suggest that 18 F-FES PET is useful for characterization of ER status of metastatic breast cancer lesions. We also review current best practices for conducting 18 F-FES PET scans. This imaging assay has potential to improve clinically relevant outcomes for patients with (historically) ER-positive metastatic breast cancer, including those with brain metastases and/or lobular histology. IMPLICATIONS FOR PRACTICE: 16α-18F-fluoro-17β-estradiol positron emission tomography (18 F-FES PET) imaging assesses estrogen receptor status in breast cancer in vivo. This work reviews the sensitivity and specificity of 18 F-FES PET in a meta-analysis with reference tissue assays and discusses best practices for use of the tracer as an imaging biomarker. 18 F-FES PET could enhance breast cancer diagnosis and staging as well as aid in therapy selection for patients with metastatic disease. Tissue sampling limitations, intrapatient heterogeneity, and temporal changes in molecular markers make it likely that 18 F-FES PET will complement existing assays when clinically available in the near future.

Application of PET Tracers in Molecular Imaging for Breast Cancer

PURPOSE OF REVIEW

Molecular imaging with positron emission tomography (PET) is a powerful tool to visualize breast cancer characteristics. Nonetheless, implementation of PET imaging into cancer care is challenging, and essential steps have been outlined in the international "imaging biomarker roadmap." In this review, we identify hurdles and provide recommendations for implementation of PET biomarkers in breast cancer care, focusing on the PET tracers 2-[18F]-fluoro-2-deoxyglucose ([18F]-FDG), sodium [18F]-fluoride ([18F]-NaF), 16α-[18F]-fluoroestradiol ([18F]-FES), and [89Zr]-trastuzumab.

RECENT FINDINGS

Technical validity of [18F]-FDG, [18F]-NaF, and [18F]-FES is established and supported by international guidelines. However, support for clinical validity and utility is still pending for these PET tracers in breast cancer, due to variable endpoints and procedures in clinical studies. Assessment of clinical validity and utility is essential towards implementation; however, these steps are still lacking for PET biomarkers in breast cancer. This could be solved by adding PET biomarkers to randomized trials, development of imaging data warehouses, and harmonization of endpoints and procedures.

Recent Advances in Imaging Steroid Hormone Receptors in Breast Cancer

Estrogen receptor (ER) and progesterone receptor (PR) are important prognostic and predictive biomarkers in breast cancer. PET using ER- and PR-specific radioligands enables a whole-body, noninvasive assessment of receptor expression. Recent investigations of ER imaging with ¹⁸F-fluoroestradiol have focused on diagnosing ER-positive metastatic disease, optimizing ER-targeted drug dosage, and predicting endocrine therapy benefit. Studies of PR imaging with ¹⁸F-fluorofuranyl norprogesterone have investigated how imaging changes in PR expression as a downstream target of ER activation may reflect an early response to ER-targeted therapy. This focused review highlights recent achievements in preclinical and clinical imaging of ER and PR in breast cancer.

18F-FES PET/CT Influences the Staging and Management of Patients with Newly Diagnosed Estrogen Receptor-Positive Breast Cancer: A Retrospective Comparative Study with 18F-FDG PET/CT

PURPOSE

We compared the clinical value of 16a-18F-fluoro-17b-estradiol (¹⁸F-FES) positron emission tomography (PET)/computed tomography (CT) and ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) PET/CT and investigated whether and how ¹⁸F-FES PET/CT affects the implemented management of newly diagnosed estrogen receptor positive breast cancer patients.

MATERIALS AND METHODS

We retrospectively analyzed 19 female patients newly diagnosed with immunohistochemistry-confirmed estrogen receptor (ER)-positive breast cancer who underwent ¹⁸F-FES and ¹⁸F-FDG PET/CT within 1 week in our center. The sensitivity of ¹⁸F-FES and ¹⁸F-FDG in diagnosed lesions were compared. To investigate the definite clinical impact of ¹⁸F-FES on managing patients with newly diagnosed ER positive breast cancer, we designed two kinds of questionnaires. Referring physicians completed the first questionnaire based on the ¹⁸F-FDG report to propose the treatment regime, and the second was completed immediately after reviewing the imaging report of ¹⁸F-FES to indicate intended management changes.

RESULTS

In total, 238 lesions were analyzed in 19 patients with newly diagnosed ER-positive breast cancer. Lesion detection was achieved in 216 sites with ¹⁸F-FES PET and in 197 sites with ¹⁸F-FDG PET/CT. These results corresponded to sensitivities of 90.8% for ¹⁸F-FES versus 82.8% for ¹⁸F-FDG PET/CT in diagnosed lesions. Thirty-five physicians were given the questionnaires referring to the treatment strategy, with 27 of them completing both questionnaires. The application of ¹⁸F-FES in addition to ¹⁸F-FDG PET/CT changed the management in 26.3% of the 19 patients with newly diagnosed ER-positive breast cancer.

CONCLUSION

Performing ¹⁸F-FES PET/CT in newly diagnosed ER-positive breast cancer patients increases the value of diagnosis equivocal lesions and treatment management compared with ¹⁸F-FDG PET/CT.

IMPLICATIONS FOR PRACTICE

This study investigated whether 16a-18F-fluoro-17b-estradiol (¹⁸F-FES) positron emission tomography (PET)/computed tomography (CT) affects the clinical management of patients with newly diagnosed estrogen receptor (ER)-positive breast cancer. Physicians completing two questionnaires comparing the clinical impact of 18F-FES and 18F-FDG on individual management plans in patients with newly diagnosed ER-positive breast cancer confirmed that 18F-FES scans led to change in management in 26.3% of the 19 patients with newly diagnosed ER positive breast cancer. This retrospective study indicates the potential impact of 18F-FES PET/CT on intended management of patients with newly diagnosed estrogen receptor positive breast cancer in comparison to 18F-fluoro-2-deoxy-D-glucose PET/CT.