As we all know, there are benign and malignant tumors. For benign tumors, as long as they are treated with thorough surgery, they can be put to an end and there is no need to worry about anything in the future. However, malignant tumors are not. The biological characteristics of malignant tumors are unlimited growth and distant metastasis, and it is likely that the cancer cells have already “flown away” during the first treatment, or are hiding in a corner, and will resurface once the immune function of the body decreases. Therefore, the discharge of malignant tumor patients from hospital after treatment is never the end of treatment, there is still a long road to go, and close follow-up is very important. Why should malignant tumor patients receive regular follow-up after discharge? Firstly, it is for early detection of tumor recurrence and metastasis. As we all know, the treatment effect of many malignant tumors is still unsatisfactory, and they still have the possibility of recurrence and or metastasis although they have undergone various treatments. If we can detect them at the early stage of recurrence or metastasis and give active treatment, many patients still have the chance to be eradicated again or continue to get long-term survival. Secondly, in order to timely detect repeat cancer and stable occult cancer. After a tumor patient receives treatment, the original cause of the tumor may not be removed and continue to occur, thus a second or even more tumors appear in the patient’s body, which is medically known as recurrent cancer. For example, many paired organs have tumors on one side, and then tumors appear on the other side or other parts of the organ. For example, patients with lung cancer, breast cancer, colorectal cancer and stomach cancer have several times higher chances of reoccurrence of malignant tumors than the normal population. There is another type of cause, certain diagnostic and treatment methods themselves can also cause cancer. For example, repeatedly receiving radioactive rays, or certain anti-cancer drugs, which were needed for diagnosis and treatment at that time, but with the joint participation of certain carcinogenic factors, later led to the emergence of repeat cancer. For example, after radiation therapy, another tumor appeared at the site of radiation therapy; lymphoma patients later developed bladder cancer due to long-term repeated treatment with the anti-cancer drug cyclophosphamide. The so-called occult cancer refers to the fact that metastatic foci are found first clinically, while the primary foci are very hidden and sometimes need a longer period of follow-up and repeated examinations by many ways before they are discovered. The timely detection of such occult cancer will play a certain role in the treatment. Thirdly, it is the continuation of comprehensive treatment at any time. The treatment of modern tumor is often comprehensive, and the combined application of various means can improve the therapeutic effect. For example, adjuvant chemotherapy and immunotherapy after surgery, Chinese herbal medicine treatment for radiotherapy, etc. Most of these adjuvant therapies are carried out in the course of follow-up. In addition, various therapeutic processes will also have one or another complications and drug toxic side effects, which also need to be observed and handled during the follow-up process. Fourthly, the scientific evaluation of various therapeutic effects must be carried out during the follow-up. Because the evaluation of tumor treatment efficacy is calculated by annual survival rate, such as 2 years, 5 years, 10 years, or even 20 years survival rate, which requires long-term follow-up of tumor patients. If a specific treatment trial is to be scientifically evaluated, more careful periodic observations and examinations are needed to determine different levels of efficacy. Without adequate follow-up information and a high rate of follow-up, its value will be significantly reduced and may even come out with wrong conclusions. So, what are the main components of the follow-up visits under physician surveillance? First of all, it is necessary to understand the whole body condition after treatment, including functional status and quality of life. The test indexes should include sleep, appetite, food intake, degree of self-care, as well as psychological and mental status, in addition to items such as body temperature, respiration, pulse, blood pressure and weight. Secondly, it is important to understand whether there is any limited recurrence or distant metastasis after treatment. This requires the follow-up doctors to make careful and comprehensive physical examination, regular measurement of certain tumor markers, B-type ultrasound, X-ray, endoscopy and isotope scan auxiliary examination of certain specific areas. For example, as primary liver cancer is prone to recurrence and distant metastasis after surgical resection, regular laboratory tests for methemoglobin and regular ultrasound and X-ray chest radiographs are necessary for early detection. Again, the complications and toxic side effects of various treatments should be followed up. If we want to know the bone marrow suppression caused by chemotherapy or radiotherapy, regular blood tests should be done; to determine the effects of chemotherapy, radiotherapy and other measures on heart, liver and kidney organs, we should do electrocardiogram, heart and liver energy, liver function, kidney function and other tests. As for the frequency and interval of follow-up after treatment of malignant tumor, it should vary with the malignancy of the tumor and the stage of the disease. The follow-up interval should be short for tumors with high malignancy and fast development. Generally speaking, within 2-3 years after malignant tumor treatment, it should be reviewed once every 2-3 months. In the 3rd to 5th year, it should be reviewed every 6 months, and after 5 years, it should be reviewed once a year until lifetime.