A Role of PET/MR in Breast Cancer?

PET/MRI has been available since 2010, representing the newest of the hybrid imaging modalities. It combines functional as well as morphologic high-resolution MRI data with metabolic information from PET, providing image data sets with complementary information. Especially in the field of oncology, PET/MRI is a promising imaging modality with diverse applications. Since its introduction there has already been a large quantity of studies indicating a high diagnostic value of PET/MRI for whole-body cancer staging. The simultaneous acquisition of metabolic PET and MRI data is expected to have a major impact in the assessment of breast cancer due to the superior resolution of MRI in breast tissue compared to CT. While there is an ongoing debate if the added value of breast ¹⁸F-FDG PET/MRI in the primary diagnosis of breast cancer has clinical impact compared to breast MRI, a large number of studies have proven that ¹⁸F-FDG PET/MRI is extremely valuable for whole-body breast cancer staging and especially for treatment monitoring. Besides molecular markers, distant metastases and axillary lymph node involvement are the most important predictors for overall survival and recurrence in breast cancer patients. Due to the high soft tissue contrast, functional imaging from MRI and metabolic information from PET, distant metastases in organs and in particular in the bones are detected better compared to the conventional staging algorithm with CT and bone scan and can significantly influence the therapy regime. Instead of mastectomy and extensive axillary dissection being performed in many patients, the improved imaging and diagnostic confidence also has helped that local therapy control can be achieved with reduced invasiveness. A future role of ¹⁸F-FDG PET/MRI could therefore become treatment response evaluation under neoadjuvant treatment before or instead of operative therapy. In addition to reduced radiation exposure compared to conventional staging examinations, hybrid ¹⁸F-FDG PET/MRI might serve as a comprehensive "all-in-one" breast cancer staging tool, providing precise local and whole-body staging including MRI of the head in one procedure, which save patients a diagnostic marathon.