This review presented the rationale of using protons in the setting of locally advanced breast cancer, which is to mitigate treatment related toxicity, especially the cardiopulmonary sequelae. Although data is limited, this review discussed early clinical results which appeared to be promising. Clinical and technical considerations on protons delivery techniques are highlighted, and three ongoing large-scale randomized studies are summarized which will provide comparative evidence to elucidate benefits of PT and guide patient selection.