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From staging to changing strategy: [18F]FDG PET/MRI's impact on treatment planning in early breast cancer.

R. di Micco S. P. Corona V. Bagnardi S. Riccardi C. Canevari F. Gallivanone L. Antunovic Paola Scifo I. Neri F. Gelardi P. Magnani C. Losio E. Venturini G. Della Vecchia G. Ferrarese N. Rotmensz V. Zuber S. Baleri G. Cisternino F. Calabretto M. Rampa Ludovica Pitoni G. Viale L. Licata I. Sassi G. Bianchini P. Panizza A. Chiti O. Gentilini

Oct 2026 · European Journal of Cancer · Vol 249, pp. 117809 · 0 citations · 37 references

Medicine

Abstract

INTRODUCTION Accurate staging at diagnosis is essential for optimizing treatment strategies and prognosis in early breast cancer (EBC). [18F]FDG positron emission tomography/magnetic resonance imaging (PET/MRI) is a hybrid imaging modality that enables simultaneous evaluation of locoregional disease and metastatic spread. This study assessed the impact of [18F]FDG PET/MRI on treatment planning in patients with EBC.

Methods

This unplanned sub-study derives from a prospective, interventional, single-arm clinical trial (SNB vs PET/MRI 2) conducted at San Raffaele University Hospital (Milan) between July 2020 and April 2024 (NCT04829643). Patients with EBC scheduled for primary surgery underwent additional preoperative [18F]FDG PET/MRI. The primary objective was the proportion of patients whose treatment strategy was modified following [18F]FDG PET/MRI findings and multidisciplinary discussion. The secondary objective was the performance of [18F]FDG PET/MRI in detecting multifocal breast cancer compared with standard imaging.

Results

A total of 264 patients were analyzed. [18F]FDG PET/MRI led to treatment plan modifications 30.7% (81/264, 95% CI: 25.4%-36.5%) of patients. Surgical approach was altered in 23.9% (63/264), while 4.9% (13/264) received primary systemic therapy and 1.9% (5/264) were referred for systemic therapy alone. [18F]FDG PET/MRI showed a sensitivity of 61.7%, specificity of 84.9%, positive predictive value (PPV) of 49.2%, and negative predictive value (NPV) of 90.4% for multifocal disease detection. When combined with standard imaging, PPV increased to 63.6%; sensitivity was 29.8%.

Conclusions

[18F]FDG PET/MRI substantially influences treatment decisions in EBC, modifying management in nearly one-third of patients. MRI was highly informative for detecting multifocal disease, whereas the potential added value of [18F]FDG PET/MRI may primarily relate to integrated axillary and distant staging. However, its moderate diagnostic accuracy warrants caution to prevent overtreatment.

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