Stage IV cancer means that distant metastasis has occurred in advanced cancer. In clinical practice, cancer patients are generally staged according to the size of cancer tumor, the number of lymph node metastasis and the presence of distant organ metastasis, which are divided into stage I, II, III and IV. The larger the tumor volume and the more lymph node metastasis, the later the cancer stage is, but regardless of the size of the tumor and the number of lymph node metastasis, patients with distant organ metastasis can be directly classified as stage IV, such as lung cancer patients with bone metastasis can be directly classified as stage IV. The later the stage is, the shorter the survival period and the worse the treatment effect.