Dr Callahan on Commonly Used Imaging Modalities in Breast Cancer

Rena D. Callahan, MD, associate professor, medicine, David Geffen School of Medicine, UCLA Health, discusses the range of metastatic imaging techniques available in breast cancer, the benefits of liquid biopsy, and the importance of looking for bone metastases in patients with metastatic breast cancer.

When looking for metastases or determining responses to treatment in patients with breast cancer, one standard imaging modality is a computed tomography (CT) scan. This could include a CT scan of the chest with contrast, or a CT scan of the abdomen and pelvis with or without contrast, Callahan says. Nuclear medicine bone scans are also a standard imaging technique, Callahan notes. These imaging modalities are generally used in clinical trials in the United States and internationally because they are widely available and often covered by insurance, Callahan explains.

Although it is not a standard imaging modality, positron emission tomography (PET)/CT scans may also be used in metastatic breast cancer because they can detect disease in the organs, lymph nodes, and bones all at once, which is often more convenient for patients, Callahan emphasizes. In addition, PET/CT scans can generally cover the base of the skull to the middle of the thigh, providing a more comprehensive look at the body when compared with a CT scan that only assesses the chest, abdomen, and pelvis, according to Callahan.

Non-bone metastatic lesions are optimal sites for biopsy in patients with metastatic breast cancer, Callahan says. However, in patients with bone-only disease, potential sites of bone lesion biopsies should be reviewed with a radiologist, who can help determine the metastatic location with the highest diagnostic yield, Callahan notes. Bone lesion sites should also be technically feasible to biopsy, Callahan emphasizes. For example, lesions in the vertebrae are difficult to biopsy, and should be avoided when possible, Callahan explains.

Since circulating tumor DNA often sheds into the bloodstream, liquid biopsy is another useful diagnostic approach that can detect targetable mutations in genes such as ESR1, according to Callahan. Liquid biopsy can often detect 3 times as many targetable mutations as bone or tissue biopsies, Callahan says.

Finding all sites of metastatic disease in a patient with breast cancer can be difficult, Callahan notes. CT scans can determine the presence of several metastatic sites, but they may not detect bone metastases. Instead, nuclear medicine bone scans, PET/CT, or magnetic resonance imaging should be used be used to determine the presence of metastases in the bone, Callahan explains. Sincepatients with bone metastases may benefit from bone-directed therapies, such as denosumab or zoledronic acid, these metastases should be determined, Callahan concludes.