Prospective Pilot Study of 18F-Fluoroestradiol PET/CT in Patients With Invasive Lobular Carcinomas

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.

[18 F]-Fluoroestradiol PET (FES-PET) and [18 F] Flurodeoxyglucose PET (FDG-PET) Imaging May Aid in Managing Therapy in Patients with Metastatic Lobular Breast Cancer

AIM

This study examines the combination of FES-PET and FDG-PET as complementary imaging for detection of metastatic ILC.

METHODS

We retrospectively evaluated FES and FDG uptake in patients with metastatic ILC from an estrogen receptor (ER) positive primary tumor. We classified lesions into three categories (FES high/FDG low, FES high/FDG high, FES low/FDG low) using SUVmax cut-off values of 1.5 for FES and 5.0 for FDG. Qualitative evaluation included examination of the difference in the extent of disease between FES and FDG.

RESULTS

Of the 38 patients, 82% had FES uptake in all tumor sites identified by FDG, with 18% lacking FES uptake in at least one lesion. Mean (range) SUVmax for FES and FDG was 4.0 (0.67-10.6) and 4.6 (1.3-12.5), respectively. The majority of ILC patients (25/38), had lesions with FES high/FDG low uptake, consistent with the strongly ER + indolent nature of ILC. Patients with disease classified as FES high/FDG low had longer median overall survival (OS) (3.2 years) and progression-free survival (PFS) (1.5 years) than FES high/FDG high (OS = 2.1 years and PFS = 0.46 years). The median overall OS for all patients was 3.0 years (95% CI 2.5, 4.8) and PFS of 1.3 years (95% CI 0.6, 2.5). 8 patients (21%) had qualitatively more extensive disease by FES-PET.

CONCLUSIONS

Our findings suggest that both FES-PET and FDG-PET can identify metastatic ILC and be useful in detecting the pattern and extent of disease. The imaging combination provides additional information for prognosis and clinical decision making, balancing suitability for endocrine therapy and aggressiveness/indolence of disease.

The Role of [18F]FES PET/CT in Breast Cancer Management: An Umbrella Review

Background/Objectives: Breast cancer (BC) is the most commonly diagnosed cancer worldwide. Estrogen receptor (ER) status is a key determinant in the diagnosis and treatment of BC. Although immunohistochemistry (IHC) is the gold standard for ER assessment, it has limitations. This umbrella review aims to evaluate the role of 16α-18F-fluoro-17β-estradiol ([18F]FES) PET/CT as a non-invasive imaging tool for assessing ER expression and its implications in BC management. Methods: A comprehensive search was conducted in PubMed/MEDLINE and Cochrane Library for systematic reviews and meta-analyses published in the last decade. Studies eligible for inclusion evaluated the diagnostic accuracy and clinical utility of [18F]FES PET/CT in BC based on a predefined research question "What is the role of fluoroestradiol ([18F]FES) PET/CT in breast cancer?". Data extraction and quality assessment were performed independently by two reviewers using the AMSTAR-2 tool. Results: Eight systematic reviews met the inclusion criteria. [18F]FES PET/CT demonstrated high sensitivity (81-94%) and specificity (78-95%) in detecting ER-positive lesions. It provided a real-time, whole-body assessment of ER expression, outperforming IHC in detecting functional ER activity. Additionally, [18F]FES PET/CT showed promise in predicting treatment response and guiding therapy decisions, particularly in metastatic settings. Conclusions: This review highlights the clinical value of [18F]FES PET/CT in BC management, offering a non-invasive alternative for ER assessment with high diagnostic accuracy. Its integration into clinical practice may enhance personalized treatment strategies for BC patients.

Beyond fluorodeoxyglucose: Molecular imaging of cancer in precision medicine

Cancer molecular imaging is the noninvasive visualization of a process unique to or altered in neoplasia, such as proliferation, glucose metabolism, and receptor expression, which is relevant to patient management. Several molecular imaging modalities are now available, including magnetic resonance, optical, and nuclear imaging. Nuclear imaging, particularly using fluorine-18-fluorodeoxyglucose positron emission tomography, is widely used in the staging and response assessment of multiple cancer types. However, at this writing, new nuclear medicine probes, especially positron emission tomography tracers, are increasingly used or are being investigated for cancer evaluation. This review focuses on these probes, their biologic targets, and the applications or potential applications for their use in the assessment of various neoplasms, including both probes available for commercial use-such as somatostatin receptor ligands in neuroendocrine tumors, prostate-specific membrane antigen ligands in prostate cancer, norepinephrine analogs in neural crest tumors like neuroblastoma, and estrogen analogs in breast cancer-and others in clinical development, such as fibroblast-activating protein inhibitors, C-X-C chemokine receptor type 4 ligands, and monoclonal antibodies targeting receptor tyrosine kinases, CD4-positive or CD8-positive tumor-infiltrating lymphocytes, tumor-associated macrophages, and cancer stem cell biomarkers. These developments represent a major step toward the integration of molecular imaging as a powerful tool in precision medicine, with an expectedly significant impact on patient management and outcome.

[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.

PET Imaging of Breast Cancer: Current Applications and Future Directions

As molecular imaging use expands for patients with breast cancer, it is important for breast radiologists to have a basic understanding of molecular imaging, including PET. Although breast radiologists may not directly interpret such studies, basic knowledge of molecular imaging will enable the radiologist to better direct diagnostic workup of patients as well as discuss diagnostic imaging with the patient and other treating physicians. Several new tracers are now available to complement imaging glucose metabolism with FDG. Because it provides a noninvasive assessment of disease status across the whole body, PET offers specific advantages over tissue-based assays. Paired with targeted therapy, molecular imaging has the potential to guide personalized treatment of breast cancer, including guiding dosing during drug trials as well as predicting and assessing clinical response. This review discusses the current established applications of FDG, which remains the most widely used PET radiotracer for malignancy, including breast cancer, and highlights potential areas for expanded use based on recent research. It also summarizes research to date on the U.S. Food and Drug Administration (FDA)-approved PET tracer 16α-18F-fluoro-17β-estradiol (FES), which targets ER, including the current guidelines from the Society of Nuclear Medicine and Molecular Imaging on the appropriate use of FES-PET/CT for breast cancer as well as areas of active investigation for other potential applications. Finally, the review highlights several of the most promising novel PET tracers that are poised for clinical translation in the near future.

Update on 18F-Fluoroestradiol

18F-16α-Fluoroestradiol (18F-FES) is a radiolabeled estrogen analogue positron emission tomography (PET) imaging agent that binds to the estrogen receptor (ER) in the nucleus of ER-expressing cells. Proof-of-concept studies of 18F-FES demonstrated expected correlation between tumoral 18F-FES-positivity on PET-imaging and ER+ status assessed on biopsy samples by radioligand binding and immunohistochemistry. After decades of study, 18F-FES PET/CT gained clinical approval in 2016 in France and 2020 in the United States for use in patients with ER+ metastatic or recurrent breast cancer. ER+ as assessed by 18F-FES PET/CT has been shown to serve as a biomarker, identifying metastatic breast cancer patients who may respond to endocrine therapy and those who are unlikely to respond. In 2023, the Society of Nuclear Medicine and Molecular Imaging (SNMMI) published Appropriate Use Criteria for 18F-FES PET/CT, identifying four indications in which use of 18F-FES PET/CT was "appropriate": (1) To assess functional ER status in metastatic lesions unfavorable to biopsy or when biopsy is nondiagnostic, (2) To detect ER status when other imaging tests are equivocal or suspicious, and at (3) initial diagnosis of metastatic disease or (4) progression of metastatic disease, for considering endocrine therapy. This article reviews the foundations of 18F-FES imaging, including normal distribution, false positives, and false negatives, and describes the most up-to-date clinical uses as well as emerging research in breast cancer and other patient populations.

Prospective investigation of amino acid transport and PSMA-targeted positron emission tomography for metastatic lobular breast carcinoma

PURPOSE

To explore the feasibility of imaging amino-acid transport and PSMA molecular pathways in the detection of metastatic breast invasive lobular carcinoma (ILC) and if there is superior detection compared to standard-of-care imaging [computed tomography (CT)/bone scan, or 18F-FDG positron-emission-tomography (PET)-CT].

METHODS

20 women with de-novo or suspected metastatic ILC underwent two PET-CT scans with 18F-fluciclovine and 68Ga-PSMA-11 on separate days. Uptake per patient and in 3 regions per patient - ipsilateral axillary lymph node (LN), extra-axillary LN (ipsilateral supraclavicular or internal mammary), or distant sites of disease - was compared to standard-of-care imaging (CT/bone scan in 13 patients and 18F-FDG PET-CT in 7 patients). Results were correlated to a composite standard of truth. Confirmed detection rate (cDR) was compared using McNemar's test. Mean SUVmax of 18F-fluciclovine and 68Ga-PSMA-11 in the most avid lesion for each true positive metastatic region and intact primary lesion were compared by t-test.

RESULTS

The cDR for standard-of-care imaging was 5/20 patients in 5/60 regions. 68Ga-PSMA-11 PET-CT detected metastasis in 7/20 patients in 7/60 regions. 18F-fluciclovine PET-CT detected metastasis in 9/20 patients in 12/60 regions. The cDR for 18F-fluciclovine PET-CT was significantly higher versus standard-of-care imaging on the patient and combined region levels, while there were no significant differences between 68Ga-PSMA-11 and standard-of care imaging. 18F-fluciclovine cDR was also significantly higher than 68Ga-PSMA-11 on the combined region level. Mean SUVmax for true positive metastatic and primary lesions with 18F-fluciclovine (n = 18) was significantly greater than for 68Ga-PSMA-11 (n = 11) [5.5 ± 1.8 versus 3.5 ± 2.7 respectively, p = 0.021].

CONCLUSION

In this exploratory trial, 18F-fluciclovine PET-CT has a significantly higher cDR for ILC metastases compared to standard-of-care imaging and to 68Ga-PSMA-11. Mean SUVmax for true positive malignancy was significantly higher with 18F-fluciclovine than for 68Ga-PSMA-11. Exploratory data from this trial suggests that molecular imaging of amino acid metabolism in patients with ILC deserves further study.

CLINICAL TRIAL REGISTRATION

Early phase (I-II) clinical trial (NCT04750473) funded by the National Institutes of Health (R21CA256280).

18F-Labeled Fluoroestradiol PET/CT: Current Status, Gaps in Knowledge, and Controversies-AJR Expert Panel Narrative Review

PET/CT using 16α-[18F]-fluoro-17β-estradiol (FES) noninvasively images tissues expressing estrogen receptors (ERs). FES has undergone extensive clinicopathologic validation for ER-positive breast cancer and in 2020 received FDA approval for clinical use as an adjunct to biopsy in patients with recurrent or metastatic ER-positive breast cancer. Clinical use of FES PET/CT is increasing but is not widespread in the United States. This AJR Expert Panel Narrative Review explores the present status and future directions of FES PET/CT, including image interpretation, existing and emerging uses, knowledge gaps, and current controversies. Specific controversies discussed include whether both FES PET/CT and FDG PET/CT are warranted in certain scenarios, whether further workup is required after negative FES PET/CT results, whether FES PET/CT findings should inform endocrine therapy selection, and whether immunohistochemistry should remain the stand-alone reference standard for determining ER status for all breast cancers. Consensus opinions from the panel include agreement with the appropriate clinical uses of FES PET/CT published by a multidisciplinary expert work group in 2023, anticipated expanded clinical use of FES PET/CT for staging ER-positive invasive lobular carcinomas and low-grade invasive ductal carcinomas pending ongoing clinical trial results, and the need for further research regarding the use of FES PET/CT for nonbreast malignancies expressing ER.

Guideline-Concordant Surgical Care for Lobular Versus Ductal Inflammatory Breast Cancer

INTRODUCTION

Quality of surgical care is understudied for lobular inflammatory breast cancer (IBC), which is less common, more chemotherapy-resistant, and more mammographically occult than ductal IBC. We compared guideline-concordant surgery (modified radical mastectomy [MRM] without immediate reconstruction following chemotherapy) for lobular versus ductal IBC.

METHODS

 Female individuals with cT4dM0 lobular and ductal IBC were identified in the National Cancer Database (NCDB) from 2010-2019. Modified radical mastectomy receipt was identified via codes for "modified radical mastectomy" or "mastectomy" and "≥10 lymph nodes removed" (proxy for axillary lymph node dissection). Descriptive statistics, chi-square tests, and t-tests were used.

RESULTS

A total of 1456 lobular and 10,445 ductal IBC patients were identified; 599 (41.1%) with lobular and 4859 (46.5%) with ductal IBC underwent MRMs (p = 0.001). Patients with lobular IBC included a higher proportion of individuals with cN0 disease (20.5% lobular vs. 13.7% ductal) and no lymph nodes examined at surgery (31.2% vs. 24.5%) but were less likely to be node-negative at surgery (12.7% vs. 17.1%, all p < 0.001). Among those who had lymph nodes removed at surgery, patients with lobular IBC also had fewer lymph nodes excised versus patients with ductal IBC (median [interquartile range], 7 (0-15) vs. 9 (0-17), p = 0.001).

CONCLUSIONS

Lobular IBC patients were more likely to present with node-negative disease and less likely to be node-negative at surgery, despite having fewer, and more frequently no, lymph nodes examined versus ductal IBC patients. Future studies should investigate whether these treatment disparities are because of surgical approach, pathologic assessment, and/or data quality as captured in the NCDB.

Estrogen Receptor-targeted PET Imaging for Breast Cancer

Two complementary patient cases are presented to highlight the importance of estrogen receptor (ER)-targeting imaging in treatment planning and selection for endocrine therapy in breast cancer patients. This article will discuss the radiopharmaceuticals and biology, imaging interpretation, and current clinical applications of ER-targeting imaging using fluorine 18 fluoroestradiol PET.

ER-Targeted PET for Initial Staging and Suspected Recurrence in ER-Positive Breast Cancer

Importance

There are insufficient data comparing 16α-18F-fluoro-17β-estradiol (FES) positron emission tomography (PET) computed tomography (CT) with standard-of-care imaging (SOC) for staging locally advanced breast cancer (LABC) or evaluating suspected recurrence.

Objective

To determine the detection rate of FES PET/CT and SOC for distant metastases in patients with estrogen receptor (ER)-positive LABC and recurrences in patients with ER-positive BC and suspected recurrence.

Design, Setting, and Participants

This diagnostic study was conducted as a single-center phase 2 trial, from January 2021 to September 2023. The study design provided 80% power to find a 20% detection rate difference. Participants included patients with ER-positive LABC (cohort 1) or suspected recurrence (cohort 2). Data were analyzed from September 2023 to February 2024.

Exposure

Participants underwent both SOC imaging and experimental FES PET/CT. When there were suspicious lesions on imaging, 1 was biopsied for histopathological reference standard to confirm presence (true positive) or absence (false positive) of malignant neoplasm.

Main Outcomes and Measures

The outcome of interest was the detection rate of FES PET CT vs SOC for distant metastases and recurrences.

Results

A total of 124 patients were accrued, with 62 in cohort 1 (median [IQR] age, 52 [32-84] years) and 62 in cohort 2 (median [IQR] age, 66 [30-93] years). In cohort 1, of 14 true-positive findings, SOC imaging detected 12 and FES detected 11 (P > .99). In cohort 2, of 23 true-positive findings, SOC detected 16 and FES detected 18 (P = .77). In 30 patients with lobular histology, of 11 true-positive findings, SOC detected 5 and FES detected 9 (P = .29). There were 6 false-positive findings on SOC and 1 false-positive finding on FES PET/CT (P = .13).

Conclusions and Relevance

In this diagnostic study with pathological findings as the reference standard, no difference was found between FES PET/CT and current SOC imaging for detecting distant metastases in patients with ER-positive LABC or recurrences in patients with ER-positive tumors and suspected recurrence. FES PET/CT could be considered for both clinical indications, which are not part of current Appropriate Use Criteria for FES PET. The findings regarding FES PET/CT in patients with lobular tumors, and for lower false positives than current SOC imaging, warrant further investigation.

Molecular Imaging of Steroid Receptors in Breast Cancer

ABSTRACT

Steroid receptors regulate gene expression for many important physiologic functions and pathologic processes. Receptors for estrogen, progesterone, and androgen have been extensively studied in breast cancer, and their expression provides prognostic information as well as targets for therapy. Noninvasive imaging utilizing positron emission tomography and radiolabeled ligands targeting these receptors can provide valuable insight into predicting treatment efficacy, staging whole-body disease burden, and identifying heterogeneity in receptor expression across different metastatic sites. This review provides an overview of steroid receptor imaging with a focus on breast cancer and radioligands for estrogen, progesterone, and androgen receptors.

Can 18F-FES PET Improve the Evaluation of 18F-FDG PET in Patients With Metastatic Invasive Lobular Carcinoma?

PURPOSE

Invasive lobular carcinoma (ILC) exhibits a low affinity for 18F-FDG. The estrogen receptor (ER) is commonly expressed in ILCs, suggesting a potential benefit of targeting with the ER probe 18F-FES in this patient population. The objective of this study was to evaluate the diagnostic performance of 18F-FES imaging in patients with metastatic ILC and compare it with that of 18F-FDG.

METHODS

We conducted a retrospective analysis of 20 ILC patients who underwent concurrent 18F-FES and 18F-FDG PET/CT examinations in our center. 18F-FES and 18F-FDG imaging were analyzed to determine the total count of tracer-avid lesions in nonbone sites and their corresponding organ systems, assess the extent of anatomical regions involved in bone metastases, and measure the SUVmax values for both tracers.

RESULTS

Among 20 ILC patients, 65 nonbone lesions were found to be distributed in 13 patients, and 16 patients were diagnosed with bone metastasis, which was distributed in 54 skeletal anatomical regions. The detection rate of 18F-FDG in nonbone lesions was higher than that of 18F-FES (57 vs 37, P < 0.001). 18F-FES demonstrated a superior ability to detect nonbone lesions in 4 patients, whereas 18F-FDG was superior in 5 patients (P > 0.05). Among 9/16 patients with bone metastasis, 18F-FES demonstrated a significant advantage in the detection of bone lesions compared with 18F-FDG (P = 0.05). Furthermore, patients with only 18F-FES-positive lesions (12/12) were administered endocrine regimens, whereas patients lacking 18F-FES uptake (2/3) predominantly received chemotherapy.

CONCLUSIONS

18F-FES is more effective than 18F-FDG in detecting bone metastasis in ILC, but it does not demonstrate a significant advantage in nonbone lesions. Additionally, the results of examination with 18F-FES have the potential to guide patient treatment plans.

Women's Health Update: Growing Role of PET for Patients with Breast Cancer

Positron Emission Tomography (PET) has been growing in usage for patients with breast cancer, due to an increased number of FDA-approved PET radiotracers pertinent to patients with breast cancer as well as increased prospective evidence for the value of these agents. The leading PET radiotracer for patients with breast cancer is 18F-fluorodeoxyglucose (18F-FDG), which measures glucose metabolism. There is prospective evidence for the use of 18F-FDG PET in systemic staging of newly diagnosed locally advanced breast cancer (stages IIB-IIIC), monitoring breast cancer treatment response, and detecting breast cancer recurrence, particularly in no special type (NST) breast cancer. 16α-18F-fluoro-17β-Fluoroestradiol (18F-FES) is a radiolabeled estrogen which evaluates estrogen receptor (ER) accessible for estrogen binding. There is prospective evidence supporting 18F-FES PET as a predictive biomarker for selecting patients with metastatic breast cancer for endocrine therapies. 18F-FES PET has also been shown to be valuable in the evaluation of ER status of lesions which are difficult to biopsy, for evaluation of ER status in lesions that are equivocal on other imaging modalities, and for selecting optimal dosage of novel ER-targeted systemic therapies in early clinical trials. Multiple investigators have suggested 18F-FES PET will have an increasing role for patients with invasive lobular breast cancer (ILC), which is less optimally evaluated by 18F-FDG PET. Sodium 18F-Fluoride (18F-NaF) evaluates bone turnover and has been effective in evaluation of malignancies which commonly metastasize to bone. In patients with metastatic breast cancer, 18F-NaF PET/CT has demonstrated superior sensitivity for osseous metastases than 99mTc-MDP or CT. In addition to these three FDA-approved PET radiotracers, there are multiple novel radiotracers currently in clinical trials with potential to further increase PET usage for patients with breast cancer.

Tata Memorial Centre Evidence Based Use of Nuclear medicine diagnostic and treatment modalities in cancer

ABSTRACT

PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.