The main method to diagnose early and late stage cancer is the extent of cancer invasion, generally there are TNM stages in oncology, TNM stage I and II are early stage cancer, while TNM stage III or IV are locally advanced or late stage cancer. the specific criteria of TNM are as follows: 1. the extent of tumor invasion, 2. the location and amount of lymph node metastasis, 3. whether there is distant metastasis. Take lung cancer as an example, for example, if the tumor is ≤3cm, there is no hilar lymph node metastasis, let alone mediastinal lymph node metastasis, or bone metastasis, liver metastasis or brain metastasis, it is early stage lung cancer, while once there is brain metastasis, bone metastasis, liver metastasis, etc., it is advanced stage lung cancer. Therefore, there are specific criteria for judging early stage and late stage of cancer, and the purpose of dividing early stage and late stage is to decide different treatments according to different stages, and also to help judge the prognosis, which is definitely much better in early stage than late stage.