The fourth stage of cancer is when the cancer has a distant spread; the cancer is working its way throughout the body and not contained in a general area, states Cancer Institute NSW. It is the final stage of cancerous growth.
Stage four cancer occurs when the cancer has spread either through lymph vessels or via blood stream, according to Cancer Institute NSW. Once in the blood stream, cancer can spread to almost anywhere within the body. It can also take root in new organs, and spread far more rapidly. The process of cancer spreading is referred to as metastasis.
Unfortunately, a stage 4 prognosis has a very grim outlook, states Mayo Clinic. While some types of cancer are more easily survived and treated, others have a very low rate of survival over five years. The five-year survival rate for lung cancer in the fourth stage, for example, is 4 percent. This means that only 1 in every 25 people will survive stage four lung cancer. Some cancers, after being treated, may come back after some time. There is a lower rate of remission if the cancer has been gone for at least five years, but there is always a chance.