Dear arnetta, The prognosis (life expectancy ) of a person with stage 4 breast cancer depends on many factors, including a person’s general health, extent of disease, response to treatment etc. With so many factors influencing a person’s prognosis, it is impossible to predict. A person even with advanced disease can live for many years. However, the person who would best be able to discuss this in regard to your mother is her oncologist who has access to all of the information about her health situation.