One of the principles of adjuvant chemotherapy for breast cancer is to start adjuvant chemotherapy as soon as possible after operation. This kind of adjuvant chemotherapy implemented early after operation is called early adjuvant chemotherapy for breast cancer. It is generally believed that it should be implemented within 2 weeks after operation, and if there are no special circumstances, it should not exceed 4 weeks at the latest, which has been confirmed in the treatment of breast cancer and colorectal cancer. In recent years, some foreign scholars have advanced the early postoperative adjuvant chemotherapy to 1 day after operation, and there are no more complications. The long-term curative effect needs further follow-up. At present, some scholars believe that the timing of chemotherapy should be as early as possible, even before surgery. This method of advancing chemotherapy time to preoperative, that is, preoperative chemotherapy method, is called "new adjuvant chemotherapy method", which is a new development of comprehensive treatment strategy for breast cancer and has certain theoretical and scientific basis. Clinical practice has also proved that it is beneficial to the treatment of breast cancer, so it is increasingly recognized and widely used in clinic. The main advantages of the new adjuvant chemotherapy method are as follows.

(1) Control the primary focus, reduce the advanced tumor as much as possible, and reduce the clinical stage, so as to facilitate surgical resection or radiotherapy.

(2) To control small metastatic lesions, cancer is often not a local disease, and the application of surgical treatment or comprehensive treatment of surgery and radiotherapy can delay the whole body treatment by 1 ~ 4 months.

Experiments show that this delay will increase the risk of tumor drug resistance. If the tumor load can be seen under the microscope, the doubling time will increase by 5 or less than 2 logarithm values, and the risk of drug-resistant mutant cells will increase by 5% ~ 95%.