LAUSR

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-[ 18 F]-fluoro-2-deoxyglucose ([ 18 F]-FDG), sodium [ 18 F]-fluoride ([ 18 F]-NaF), 16α-[ 18 F]-fluoroestradiol ([ 18 F]-FES), and [ 89 Zr]-trastuzumab. Recent Findings Technical validity of [ 18 F]-FDG, [ 18 F]-NaF, and [ 18 F]-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. Summary 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.