The basic views on the relationship between chemotherapy and prognosis of breast cancer in the last 30 years: 1. High risk factors for recurrence and metastasis of breast cancer include large lesions, positive lymph nodes, hormone insensitivity, HER-2 positive and/or triple negative breast cancer; 2. Patients with more than 4 lymph node metastases are more likely to recur and metastasize than those with less than 4 lymph node metastases, 81.5% of which are distant; 3. CMF is beneficial in terms of disease-free survival/overall survival; 4. The intensity of chemotherapy needs to be at least 85% of the standard dose (efficacy is dose-related); 5. anthracycline-based regimens improve disease-free survival/overall survival compared with anthracycline-free regimens; 8. Adding paclitaxel to anthracyclines further improves disease-free survival/overall survival; 9. 2-week AC→T dose-density regimens are tolerated with better efficacy than 3-week AC→T regimens; 10. Survival.