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Understanding Metastatic Breast Cancer

What is metastatic breast cancer (MBC)?

Metastatic breast cancer occurs when breast cancer cells travel from the breast to another part of the body such as the bones, liver, lungs, or brain. MBC is also referred to as Stage IV breast cancer.

A second breast cancer that develops in the same or the other breast is not metastatic breast cancer. And having cancer cells in the lymph nodes does not mean your cancer is Stage IV, although pathologists sometimes use the term “metastatic to the lymph nodes.”

What does it mean to have metastatic breast cancer (MBC)?

A diagnosis of MBC can be very frightening because it is considered to be incurable. But as treatments improve, those diagnosed with metastatic breast cancer are living longer and able to have a better quality of life. Living with MBC usually involves ongoing treatment — chemotherapy, hormonal treatment, targeted therapy, immunotherapy or radiation.

When is metastatic breast cancer (MBC) usually diagnosed?

Some women (about six percent) are initially diagnosed at Stage IV. They may already have symptoms such as pain or shortness of breath that cause the doctors to suspect metastatic cancer or the metastasis may be discovered during a CT or PET scan as part of the initial workup for breast cancer.

Most people who become metastatic are diagnosed later, anytime from several months to years after they were initially treated for early stage cancer.

What causes metastatic breast cancer (MBC)?

It is not fully understood why some cancers become metastatic, especially those that are diagnosed years after the first breast cancer. In the past, doctors believed that cancer progressed in a linear manner and that women with positive lymph nodes were more likely to become metastatic. Now researchers are focusing more on genetics and the microbiology of breast cancer. They are trying to learn why some cancers behave more aggressively, what causes cancer cells to grow in different parts of the body, and what treatments can be developed to stop that process.

What should individuals with metastatic breast cancer (MBC) know?

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