This study is a prospective, open-label, phase II clinical trial, aiming to explore the predictive effect of different specific tracers on the effectiveness of various systemic treatments for breast cancer. The unique feature of this study is that it is a platform study. The research cohort can be updated accordingly as specific tracers for PET/MRI and systemic treatment regimens for breast cancer are updated. The study will be divided into two treatment cohorts: neoadjuvant therapy and salvage therapy. The research cohort will be further subdivided based on specific treatment regimens and specific tracers for PET/MRI. The subjects will undergo one 18F-FDG PET/MRI and specific tracer PET/MRI examination at baseline (before treatment) and after 2 treatment courses. This study is an exploratory phase II clinical trial, and its main purpose is to screen valuable cohorts for subsequent larger-sample randomized controlled III-phase clinical studies.