Breast cancer is a leading cause of cancer-related death in women, second only to lung cancer, according to the U.S. Centers for Disease Control and Prevention. The most aggressive and severe form of breast cancer is stage IV, where breast cancer becomes metastatic.
A metastatic cancer is one that has spread to other parts of the body, according to the National Cancer Institute. For breast cancer, doctors give stage IV designation to tumours in the breast that are metastatic.
Breast cancer occurs when cells within the breast undergo a DNA mutation that causes them to grow uncontrollably. In metastatic stage IV breast cancer, the cancerous cells travel to other parts of the body through the bloodstream or the lymphatic system, which is a group of structures in the body with immune-system properties.
When stage IV metastatic breast cancer spreads to other areas in the body, it causes secondary cancers, or a new tumour growth in another area, such as the lungs, bones, liver or brain.
In patients with stage IV metastatic breast cancer, doctors employ either chemotherapy to destroy cancer cells in the breast as well as in the site of the secondary cancer or hormone suppressant medications that slow the growth of some cancers that are fed by the effects of oestrogen. Rarely, doctors are able to use surgical procedures followed by radiation to treat stage IV metastatic breast cancer, according to the American Cancer Society.
Only 20 per cent of women with stage IV metastatic breast cancer survive five years after receiving a cancer diagnosis, according to the American Cancer Society.
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