Chemotherapy intervals longer than 21 days may result in chemotherapy failure or tumor progression. The usual cycle of chemotherapy is to choose a three-week or four-week regimen, so it is usually no more than 21 days or no more than 28 days. If the interval exceeds the specified time, the patient will be in the state of no treatment, which will have an impact on the effect of chemotherapy, and the tumor cells will be easy to develop resistance to chemotherapy drugs or malignant tumor cells will be easy to develop resistance to chemotherapy and so on, which will easily lead to the progression of the tumor. Different types of tumors have different chemotherapy intervals, which need to be evaluated in combination with the patient’s chemotherapy regimen, physical condition, pathological type and so on. It is recommended that patients follow the prescribed time for chemotherapy under the guidance of doctors to avoid delaying the condition.