Systemic treatment in breast cancer: a primer for radiologists

Cytotoxic chemotherapy, hormonal therapy and molecular targeted therapy are the three major classes of drugs used to treat breast cancer. Imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), 18F-FDG positron emission tomography (PET)/CT and bone scintigraphy each have a distinct role in monitoring response and detecting drug toxicities associated with these treatments. The purpose of this article is to elucidate the various systemic therapies used in breast cancer, with an emphasis on the role of imaging in assessing treatment response and detecting treatment-related toxicities. Teaching Points • Cytotoxic chemotherapy is often used in combination with HER2-targeted and endocrine therapies. • Endocrine and HER2-targeted therapies are recommended in hormone-receptor- and HER2-positive cases. • CT is the workhorse for assessment of treatment response in breast cancer metastases. • Alternate treatment response criteria can help in interpreting pseudoprogression in metastasis. • Unique toxicities are associated with cytotoxic chemotherapy and with endocrine and HER2-targeted therapies.