Molecular breast imaging. Positron emission tomography/magnetic resonance imaging and targeted tracers

Background: Molecular imaging has been introduced into breast imaging in recent years, in order to improve breast cancer (BC) depiction as well as our understanding of cancer-associated processes at a cellular and molecular level. Objectives: This review offers an overview of the various molecular imaging modalities implemented in breast imaging as well as of the most significant novel radiotracers and their potential role for the functional evaluation of BC. Materials and methods: The applications and the diagnostic potential of different imaging modalities (scintimammography [SM], breast-specific gamma imaging [BSGI], positron emission tomography [PET] mammography [PEM] and PET/MRI) as well as specific tracers (18-fluormisonidazole [F-18-MISO], 18-fluoro-L-thymidine [(FLT)-F-18], (18)fluoroestradiol [(FES)-F-18], 89-zirconium-trastuzumab, 18-Fluoroethylcholine [(FEC)-F-18] and 68-gallium-fibroblast activation protein inhibitor [68Ga-FAPI]) will be discussed. Results: BSGI increases the sensitivity of SM for small (<1 cm) lesions, while PEM is more sensitive than whole-body PET scans. Hybrid PET/MRI is the most promising imaging modality for the assessment of BC. While F-18-FDG illustrates the glucose metabolism of cancer cells, novel tracers have other, tumor-specific targets: F-18-MISO assesses tumor hypoxia,(FLT)-F-18 the metabolism of DNA, 18FES and 89Zr-trastuzumab the tumor receptor status,18FEC the metabolism of choline and 68Ga-FAPI cancer-associated fibroblasts. Conclusion: It can be expected that molecular imaging will gain importance for breast imaging in the future, enabling an improved diagnosis, staging, and treatment followup.