The purpose of postoperative adjuvant chemotherapy is to reduce recurrence and prolong patients’ progression-free survival time. Since the tumor was radically removed after surgery and systematic lymph node dissection was performed at the same time, no lymph node metastasis occurred, so considering the benefits and possible side effects of chemotherapy, postoperative adjuvant chemotherapy is not recommended for early-stage cancer. For example, breast cancer, lung cancer and intestinal cancer, if there is no lymph node metastasis and the tumor is relatively small, such as lung cancer tumor <3cm, breast cancer tumor <2cm and colorectal cancer invasion within the mucosal layer, they are all early stage cancers, because the tumor is relatively small, the invasion depth is relatively shallow and no lymph node metastasis occurs, so adjuvant chemotherapy is not needed for early stage cancers after surgery.