Chemotherapy for more than 30 days does not usually have a significant effect. However, supplemental chemotherapy needs to be administered as soon as possible. In clinical practice, chemotherapy is still the cornerstone of the treatment of malignant tumors, and a typical chemotherapy regimen has a cycle of 21 days. When the normal cells of the human body recover with the extension of time, the tumor cells will recover accordingly, which may bring some adverse effects on the treatment of tumors. In the clinic, it is necessary to choose the treatment plan according to the specific program or follow the cycle to avoid problems such as tumor resistance and tumor progression. If the interval is too long, it may affect the effect of chemotherapy. If the interval is too long after stopping the drug, the tumor will have the risk of recurrence, in which case the effect of chemotherapy will be greatly reduced, so if there is no obvious bone marrow suppression or the physical condition is too poor to tolerate the situation, it is generally necessary to follow the doctor’s instructions and do the chemotherapy once every 21 days, do not delay too long.