In the treatment of malignant tumors, systemic chemotherapy (chemotherapy for short) can successfully shrink or even eliminate tumor masses or even cure the disease, but it can also damage normal cells in the body and bring adverse effects such as vomiting, hair loss and white blood cell drop. Therefore, the art of chemotherapy is to maximize the effectiveness and minimize the toxicity, i.e., “adequate dosing and timely discontinuation”. How long is the best duration of chemotherapy? This depends on three factors: the nature of the tumor, the patient’s physical condition, and the therapeutic drug. First, some tumors with rapid cell proliferation, such as certain highly malignant lymphomas, small cell lung cancer, testicular seminoma, and choriocarcinoma. These tumors are fast-growing, sensitive to drugs, and easily “destroyed” by chemotherapy, which is characterized by “advancement or retreat”. Chemotherapy is the main treatment tool for these tumors, and the treatment should be started to “eliminate the evil”. If stopped in the middle of the treatment and allowed to return, it will often induce the tumor’s resistance to drugs, and it will be difficult to control completely. Therefore, the principle of treatment should be “if you don’t treat it, you should treat it, but if you treat it, it must be enough”, and if the physical condition allows, you must give enough consolidation chemotherapy to strive for recovery. In contrast to the above, there are other types of tumors whose cells do not proliferate rapidly and are not sensitive to chemotherapy: for example, hepatocellular carcinoma and renal clear cell carcinoma. Even if the dose is increased and the duration is prolonged, I am afraid that the toxicity will increase more and the efficacy will increase less, which will add to the pain and economic burden. Therefore, the principle of chemotherapy should be “to relieve pain, to the point”, i.e. chemotherapy is often used to suppress tumors when they progress wildly and to relieve patients’ pain, but not as a means to strive for a complete cure. Chemotherapy is rarely used alone for such tumors, but in combination with targeted and immunotherapy for best results. Then, for most other tumors that fall between the above two in nature, such as non-small cell lung cancer, breast cancer and gastrointestinal tract tumors such as gastric, esophageal and colorectal cancers and reproductive system tumors such as ovarian cancer, what kind of chemotherapy makes the most sense? The situation is more complicated at this point. First of all, if the patient has been operated and the main tumor has been removed, the role of the drug is to remove the scattered tumor cells that may remain in the body, the chemotherapy at this time is called “adjuvant chemotherapy”, and the duration of the drug after surgery should not be extended indefinitely, but there should be a reasonable time limit to ensure that it is not only “basic insurance” for the patient, but also does not cause any damage to the patient. The duration of postoperative chemotherapy should not be extended indefinitely, but should have a reasonable time limit to ensure that it is “basic insurance” for the patient and does not cause excess pain. Through a long period of time, a large number of cases and lessons learned, some rules have been identified, such as: 4-6 cycles of chemotherapy for non-small cell lung cancer and 6-8 cycles of chemotherapy for ovarian cancer. On the contrary, if the tumor has “high risk factors”, such as high malignancy, late clinical stage and fast growth, more cycles of chemotherapy will be needed. The “high risk factors” of various tumors are different and have some commonalities, so timely detection and correct assessment of them is one of the essentials of chemotherapy. With the development of science and technology, some “markers” have been discovered that can indicate tumor recurrence and metastasis at an early stage, and their dynamic observation can also help to assess the risk of recurrence and decide whether to stop or continue chemotherapy. In addition, more sophisticated imaging methods (e.g. PET CT) can also help to detect small metastases or residual lesions earlier. For tumors that have recurred or metastasized after surgery or cannot be removed at the time of consultation, chemotherapy is often used to shrink and stabilize the tumor for long-term maintenance. The chemotherapy at this time is called “palliative chemotherapy”. In fact, it is difficult to specify the duration of palliative chemotherapy, because this kind of chemotherapy will be carried out in “human tumor coexistence”, and the purpose is to suppress (not destroy) the tumor in the long term, so that it will be in a balanced and stable state with the human body. Therefore, its general principle should be “suppressing tumor development, maintaining long-term stability, and ensuring quality of life”, i.e. active treatment when tumor is developing, and reducing, postponing or even suspending chemotherapy when tumor is stable. So, is it true that “chemotherapy does not stop while life lasts”? This is not true either. Especially with the emergence of new drugs such as gene targeting therapy and anti-angiogenic agents with unique anti-tumor effect and less toxic side effects, the efficacy of liver cancer, lung cancer, gastrointestinal tract cancer and other tumors has been greatly improved, and the modern treatment is also developing into the mode of suppressing rapid tumor growth with chemotherapy and maintaining long-term stability with new drugs, so that “fast drugs are used quickly and slow drugs are used slowly. “In order to obtain the maximum anti-tumor effect, the minimum toxic side effects and the best quality of life, the advantages are complementary and mutually beneficial. To sum up, the question of “how long should chemotherapy be given” should be “different from person to person, from disease to disease, and from drug to drug”, and cannot be generalized. In other words, it is advisable to “pursue” when it can be cured, and to “maintain” when it needs to be maintained, along with immune support, palliative reduction, psychological care and other means. Every doctor should also remember that the task of modern treatment is not simply to “cure”, but to “sometimes cure, often help, always comfort”, so that the patient can get the most comprehensive dialectical treatment throughout the entire period of illness, and become a good doctor who can In this way, the patient can receive the most comprehensive treatment throughout the entire period of illness, and he or she can become a good doctor who can see the patient clearly.