Stage IV cancer does not necessarily mean death, nor is it a certainty that patients found to have stage IV cancer will die, but it also depends on the follow-up treatment and which type of cancer. Some stage IV cancers are advanced, but there are still some treatment methods, for example, brain metastasis of lung adenocarcinoma, although it is stage IV, it can still be controlled by chemotherapy and brain radiotherapy respectively. Genetic testing can also be done to see if there are any genetic mutations, and if treatment can be done with targeted drugs, it is possible to survive for a longer period of time, for example, more than 3 or 5 years. Others, such as papillary thyroid cancer stage IV with metastasis, also have a chance of treatment, such as thyroid cancer clearance plus post-operative iodine-131, the treatment effect is better. It does not necessarily lead to death immediately, but can only be seen while being treated.