Metastatic breast cancer is breast cancer that has spread to other sites, most frequently (but not exclusively) bone, lung, liver or brain. It is still breast cancer, even though it is now in another part of the body.
Metastatic breast cancer is also called Stage IV or advanced breast cancer.
Metastatic breast cancer can be diagnosed from the very beginning, or it can appear years after the initial diagnosis. About 30% of people who are diagnosed with breast cancer at any stage will develop metastatic breast cancer at some point.* No one dies of breast cancer that remains in the breast; people who die of breast cancer die of metastatic breast cancer and its complications.
Metastatic breast cancer is not an automatic death sentence. Although no cure is available at this time, there are many treatments that can extend life. Some of these treatments involve side effects that are very difficult to bear, but some are much easier to handle. It is up to everyone who is living with the disease to decide what he or she wants to do.
* “As an initial presentation, metastatic breast cancer (MBC) is uncommon, occurring in only about 6% of newly diagnosed cases. Despite advances in the treatment of breast cancer, approximately 30% of women initially diagnosed with earlier stages of breast cancer eventually develop recurrent advanced or metastatic disease.” Joyce O’Shaughnessy, MD “Extending Survival with Chemotherapy in Metastatic Breast Cancer” in The Oncologist 2005:10. Retrieved from online archive.