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-17ß-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.

Quarter-Century Transformation of Oncology: Positron Emission Tomography for Patients with Breast Cancer.

PET radiotracers have become indispensable in the care of patients with breast cancer. 18F-fluorodeoxyglucose has become the preferred method of many oncologists for systemic staging of breast cancer at initial diagnosis, detecting recurrent disease, and for measuring treatment response after therapy. 18F-Sodium Fluoride is valuable for detection of osseous metastases. 18F-fluoroestradiol is now FDA-approved with multiple appropriate clinical uses. There are multiple PET radiotracers in clinical trials, which may add utility of PET imaging for patients with breast cancer in the future. This article will describe the advances during the last quarter century in PET for patients with breast cancer.

Summary: SNMMI Procedure Standard/EANM Practice Guideline for Estrogen Receptor Imaging of Patients with Breast Cancer Using 16α-[18F]Fluoro-17ß-Estradiol PET.

The estrogen receptor (ER), a steroid hormone receptor important in female physiology, is a significant contributor to breast carcinogenesis and progression and, as such, is an important therapeutic target. Approximately 70% of breast cancers will express ER at presentation, and the determination of ER expression by tissue assay, usually by immunohistochemistry, is part of the standard of care for newly diagnosed breast cancer. ER expression is important in guiding the approach to treatment, especially with the increase in relevant systemic therapies. The ER-targeting imaging agent 16α-[18F]fluoro-17ß-estradiol ([18F]FES) is approved for clinical use by regulatory agencies in France and the United States. Multiple studies suggest the advantages of [18F]FES PET in assessing tumor ER expression, the ability of both qualitative and quantitative [18F]FES PET measures to predict response to ER-targeted therapy, and the ability of [18F]FES PET to clarify equivocal staging and restaging results in patients with ER-expressing cancers. [18F]FES PET/CT may also be helpful in staging invasive lobular breast cancer and low-grade ER-expressing invasive ductal cancers and, in some cases, may be a substitute for biopsy. The Society of Nuclear Medicine and Molecular Imaging and the European Association of Nuclear Medicine in June 2023 released a procedure standard/practice guideline for [18F]FES PET ER imaging of patients with breast cancer. The goal of the standard/guideline is to assist physicians in recommending, performing, interpreting, and reporting the results of [18F]FES PET studies for patients with breast cancer and to provide clinicians with the best available evidence, inform them about areas where robust evidence is lacking, and help them deliver the best possible diagnostic efficacy and study quality for their patients. Also reviewed are standardized quality control, quality assurance, and imaging procedures for [18F]FES PET. The authors emphasize the importance of precision, accuracy, repeatability, and reproducibility for both clinical management of patients and for use of [18F]FES PET in multicenter trials. A standardized imaging procedure, in combination with already published appropriate-use criteria, will help promote the use of [18F]FES PET and enhance subsequent research. This brief summary article reviews the content of the joint standard/guideline, which is available in its entirety at https://www.snmmi.org/ClinicalPractice/content.aspx?ItemNumber=6414&navItemNumbe=10790.