Stage 4 kidney cancer is the fourth and final stage of development of the cancer, so it's very serious. In stage 4 kidney cancer, the tumor on the kidney may be any size, often very large. At this stage, the cancer has spread to other parts of the body. Generally, the first areas outside the kidney that are affected are nearby lymph nodes and the major veins connected to the kidneys, but by stage 4, it has often reached distant organs. This means that treatment for stage 4 kidney cancer is complex since it has to address cancer that's not contained within the kidney. This kind of treatment isn't often possible, so stage 4 kidney cancer is usually fatal. The five-year survival rate for stage 4 cancer (meaning the percentage of people who, after treatment, will live at least five years following diagnosis) is only 8%.