Stage I cancer is very early and may not need chemotherapy, such as early stage I breast cancer or esophageal cancer, etc. Regular review and observation are sufficient. Especially, esophageal cancer is not too sensitive to chemotherapy itself, so chemotherapy can be dispensed with. However, in the case of breast cancer, there are applications of chemotherapy, such as adjuvant chemotherapy, which has the effect of preventing recurrence and metastasis. If stage I cancer has local infiltrative manifestation and may have recurrence or metastasis in other parts, it is better to suggest 4-6 courses of adjuvant chemotherapy. Therefore, whether chemotherapy is needed or not is decided according to the analysis and communication opinion of the patient and also the treating doctor. If the advantages outweigh the disadvantages, it is better to choose chemotherapy. Chemotherapy can cause some side effects, such as nausea, vomiting, white blood cell drop, etc., which can be relieved by symptomatic treatment.