Metastatic Breast Cancer (MBC) is breast cancer that has spread outside of the breast and lymph nodes underneath the arm (axillary lymph nodes) and moved into other parts of the body. When MBC is detected after the breast cancer was initially diagnosed and treated, it is called recurrent breast cancer.

When breast cancer recurs, patients will undergo testing to see the extent of the breast cancer recurrence. This may involve imaging studies such as PET scans, CT scans and bone scans.

If at all possible, tissue will be obtained from an area of recurrence. The recurrent breast cancer will be tested to see if it is sensitive to hormone blocking medication and/or HER2 targeted medications. It may also undergo additional testing to predict whether it may respond to chemotherapy agents (genomic testing). Testing is done because the recurrent breast cancer’s biology may have changed from the initial breast cancer. Just like bacteria can become resistant to specific antibiotics, some cancer cells may develop resistance to medications.

For example, a patient’s breast cancer may have been initially sensitive to estrogen (estrogen receptor positive) and their recurrent breast cancer has become resistant to estrogen (estrogen receptor negative). For this patient, estrogen blocking therapy will not be helpful.

Another patient’s initial breast cancer may have been unresponsive to HER2 targeted medications (HER2 negative) but their breast cancer recurrence is responsive to HER2 targeted medications (HER2 positive). This patient would benefit from such HER2 targeted therapy using Trastuzumab (Herceptin) and Pertuzumab (Perjeta).

Depending on the location and extent of the metastatic breast cancer, as well as symptoms caused by the metastatic breast cancer, surgery and/ or radiation may be offered. Surgery removing metastatic breast cancer is usually limited to patients who have very isolated metastases that have occurred a long time after their initial breast cancer diagnosis. Radiation therapy is often used to target bone metastases that are causing pain or threat of spinal cord damage.

Treatment of MBC is personalized to each patient based on their goals and options that will be of potential benefit in their specific case. Individual patients will work with their health care team to create their own treatment plan.