To investigate the feasibility of whole-body 18F-FDG PET/MRI including an integrated breast MRI protocol in breast cancer patients for locoregional and distant staging.

Patients diagnosed with histopathologically confirmed breast cancer according to conventional imaging modalities (i.e. mammography and ultrasound) were prospectively included. All patients were considered for further examination with regard to locoregional and distant staging and underwent whole-body 18F-FDG PET/MRI including an integrated breast MRI protocol. The protocol consisted of dedicated breast MRI (prone position) and whole-body PET/MRI (supine position; including T2W, T1W post-contrast, DWI sequences and PET reconstructions) approximately 60 minutes after injection of 18F-FDG. In addition, unenhanced chest CT was performed for pulmonary lesion detection. Results of 18F-FDG PET/MRI, including integrated breast MRI, were compared to conventional imaging modalities in terms of clinical tumour (cT), nodal (cN) and distant (cM) status, according to 8th edition of TNM classification.

From April 2021 until April 2022, 26 breast cancer patients were included and underwent whole-body 18F-FDG PET/MRI including an integrated breast MRI protocol.According to conventional imaging, cT1-2 breast cancer was present in 22 out of 26 patients, 3 patients had cT3 and one patient cT4 breast cancer. With regard to cN status, 9 patients were considered cN0, 15 cN1 (1-3 suspicious lymph nodes) and 2 patients cN2-3 (four or more suspicious lymph nodes). Whole-body 18F-FDG PET/MRI, including an integrated breast MRI protocol, upstaged cT status in ten patients and cN status in nine patients. In addition, distant metastases were detected in three patients and a fourth patient was diagnosed with a synchronous primary tumour (lung cancer).

Whole-body 18F-FDG PET/MRI amended by an integrated breast MRI protocol ifeasible and upstagelocoregional and distant statuin a considerable amount of recently diagnosed breast cancer patientwith an indication for whole body staging.

Whole-body 18F-FDG PET/MRI amended by an integrated breast MRI protocol provides a promising new approach in breast cancer patients with regard to locoregional and distant staging.