Local and whole-body staging in patients with primary breast cancer: a comparison of one-step to two-step staging utilizing 18 F-FDG-PET/MRI.

Objectives: The purpose of this study was to compare the diagnostic value of a one-step to a two-step staging algorithm utilizing ¹⁸ F-FDG PET/MRI in breast cancer patients.
Methods: A total of 38 patients (37 females and one male, mean age 57 ± 10 years; range 31-78 years) with newly diagnosed, histopathologically proven breast cancer were prospectively enrolled in this trial. All PET/MRI examinations were assessed for local tumor burden and metastatic spread in two separate reading sessions: (1) One-step algorithm comprising supine whole-body ¹⁸ F-FDG PET/MRI, and (2) Two-step algorithm comprising a dedicated prone ¹⁸ F-FDG breast PET/MRI and supine whole-body ¹⁸ F-FDG PET/MRI.
Results: On a patient based analysis the two-step algorithm correctly identified 37 out of 38 patients with breast carcinoma (97%), while five patients were missed by the one-step ¹⁸ F-FDG PET/MRI algorithm (33/38; 87% correct identification). On a lesion-based analysis 56 breast cancer lesions were detected in the two-step algorithm and 44 breast cancer lesions could be correctly identified in the one-step ¹⁸ F-FDG PET/MRI (79%), resulting in statistically significant differences between the two algorithms (p = 0.0015). For axillary lymph node evaluation sensitivity, specificity and accuracy was 93%, 95 and 94%, respectively. Furthermore, distant metastases could be detected in seven patients in both algorithms.
Conclusion: The results demonstrate the necessity and superiority of a two-step ¹⁸ F-FDG PET/MRI algorithm, comprising dedicated prone breast imaging and supine whole-body imaging, when compared to the one-step algorithm for local and whole-body staging in breast cancer patients.