Lung cancer is generally stage IV if it metastasizes to the brain, which is the last stage, because lung cancer has four stages in total: I, II, III and IV, which is actually the most advanced stage. Generally speaking, as long as lung cancer patients have distant metastasis, it is considered stage IV. If it metastasizes to important organs, such as brain, liver and other more important organs, not only is it stage IV, but it also indicates a very bad prognosis and the patient’s survival period will be very short. Generally, patients with cranial metastases will probably have a final survival period of about three months.