To plan optimal management in a patient with breast cancer (BC), accurate baseline staging and early detection and staging of recurrence are necessary.1-3 Representatives from the European Association of Nuclear Medicine (EANM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) recently published the joint European-American guidelines on the role of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) in no special type (NST) BC, endorsed by several other imaging and clinical societies: the American College of Radiology (ACR), European Society of Surgical Oncology, European Society for Radiotherapy and Oncology (ESTRO), European Society of Breast Imaging, European Society of Radiology, and European Society of Breast Cancer Specialists (EUSOMA).1 Considering the low [18F]FDG-avidity in invasive lobular carcinoma (ILC), the EANM-SNMMI guidelines focused on NST BC. Guidelines from clinical societies such as the American National Comprehensive Cancer Network (NCCN),4 European Society for Medical Oncology (ESMO),5-7 and Advanced Breast Cancer (ABC) international consensus guidelines8 also evaluate imaging techniques, but they include all histological subtypes of BC. There is a lack of consistency in the optimal utilization of [18F]FDG-PET/CT among published guidelines. This manuscript summarizes available evidence, emphasizes the value of [18F]FDG-PET/CT for staging and restaging of patients with BC, and highlights agreements and discrepancies among international guidelines.

Introduction: There is much literature about the role of 2-[¹⁸F]FDG PET/CT in patients with breast cancer (BC). However, there exists no international guideline with involvement of the nuclear medicine societies about this subject. Purpose: To provide an organized, international, state-of-the-art, and multidisciplinary guideline, led by experts of two nuclear medicine societies (EANM and SNMMI) and representation of important societies in the field of BC (ACR, ESSO, ESTRO, EUSOBI/ESR, and EUSOMA). Methods: Literature review and expert discussion were performed with the aim of collecting updated information regarding the role of 2-[¹⁸F]FDG PET/CT in patients with no special type (NST) BC and summarizing its indications according to scientific evidence. Recommendations were scored according to the National Institute for Health and Care Excellence (NICE) criteria. Results: Quantitative PET features (SUV, MTV, TLG) are valuable prognostic parameters. In baseline staging, 2-[¹⁸F]FDG PET/CT plays a role from stage IIB through stage IV. When assessing response to therapy, 2-[¹⁸F]FDG PET/CT should be performed on certified scanners, and reported either according to PERCIST, EORTC PET, or EANM immunotherapy response criteria, as appropriate. 2-[¹⁸F]FDG PET/CT may be useful to assess early metabolic response, particularly in non-metastatic triple-negative and HER2+ tumours. 2-[¹⁸F]FDG PET/CT is useful to detect the site and extent of recurrence when conventional imaging methods are equivocal and when there is clinical and/or laboratorial suspicion of relapse. Recent developments are promising. Conclusion: 2-[¹⁸F]FDG PET/CT is extremely useful in BC management, as supported by extensive evidence of its utility compared to other imaging modalities in several clinical scenarios.