The EC regimen for breast cancer chemotherapy refers to the use of two chemotherapy drugs, epirubicin and cyclophosphamide. An EC regimen for breast cancer is a commonly used chemotherapy administration regimen, where E refers to epirubicin and C refers to cyclophosphamide. In chemotherapy regimens, injections of both drugs are typically used. Epirubicin hydrochloride for injection is mainly used for the treatment of malignant lymphoma, breast cancer, soft tissue sarcoma and other diseases, and common adverse reactions include cardiotoxicity, myelosuppressive toxicity, alopecia, mucositis, nausea and vomiting. The drug is contraindicated in patients with significant myelosuppression, patients who have used high doses of anthracyclines (e.g., doxorubicin, etc.), and patients with cardiac compromise. Cyclophosphamide for injection is mainly used to treat leukemia, malignant lymphoma, ovarian cancer, breast cancer and other diseases. Common adverse reactions include infection, myelosuppression, neutropenia, thrombocytopenia, and anemia. It is contraindicated in people who are allergic to the drug, people with severe bone marrow impairment, cystitis, urinary tract obstruction, acute infections, pregnant and lactating women. The combination of the two drugs is used as an adjunctive program for the treatment of patients. During the period of treatment, changes in blood routine and liver and kidney functions should be checked regularly, and if there are any abnormal symptoms, the doctor should be notified in time for appropriate treatment.