Impact of ¹⁸F-FDG PET/MRI on Therapeutic Management of Women with Newly Diagnosed Breast Cancer: Results from a Prospective Double-Center Trial

Our rationale was to investigate whether ¹⁸F-FDG PET/MRI in addition to (guideline-recommended) conventional staging leads to changes in therapeutic management in patients with newly diagnosed breast cancer and compare the diagnostic accuracy of ¹⁸F-FDG PET/MRI with that of conventional staging for determining the Union for International Cancer Control (UICC) stage. Methods: In this prospective, double-center study, 208 women with newly diagnosed, therapy-naïve invasive breast cancer were enrolled in accordance with the inclusion criteria. All patients underwent guideline-recommended conventional staging and whole-body ¹⁸F-FDG PET/MRI with a dedicated breast examination. A multidisciplinary tumor board served to determine 2 different therapy recommendations for each patient, one based on conventional staging alone and another based on combined assessment of conventional staging and ¹⁸F-FDG PET/MRI examinations. Major changes in therapy recommendations and differences between the conventional staging algorithm and ¹⁸F-FDG PET/MRI for determining the correct UICC stage were reported and evaluated. Results: Major changes in therapeutic management based on combined assessment of conventional staging and ¹⁸F-FDG PET/MRI were detected in 5 of 208 patients, amounting to changes in therapeutic management in 2.4% (95% CI, 0.78%-5.2%) of the study population. In determining the UICC stage, the guideline-based staging algorithm and ¹⁸F-FDG PET/MRI were concordant in 135 of 208 (64.9%; 95% CI, 58%-71.4%) patients. The conventional guideline algorithm correctly determined the UICC stage in 130 of 208 (62.5%; 95% CI, 55.5%-69.1%) patients, and ¹⁸F-FDG PET/MRI correctly determined the UICC stage in 170 of 208 (81.9%; 95% CI, 75.8%-86.7%) patients. Conclusion: Despite the diagnostic superiority of ¹⁸F-FDG PET/MRI over conventional staging in determining the correct UICC stage, the current (guideline-recommended) conventional staging algorithm is sufficient for adequate therapeutic management of patients with newly diagnosed breast cancer, and ¹⁸F-FDG PET/MRI does not have an impact on patient management.