A person with stage 4 primary breast cancer that is metastatic has a five-year survival rate of 22 percent, explains the American Cancer Society. Stage 4 metastatic breast cancer is cancer that has spread to other areas of the body such as bones, lungs, liver or brain.
Breast cancer that is stage 4 is not curable as of 2015, but treatment can improve both the quality and longevity of life, according to Healthline. Not all people react to cancer treatment in the same way. Many factors such as age, hormone receptor status, overall health and staging of cancer affect a person's survival rates.