The regimen for the use of DS8201 in the treatment of breast cancer is 5.4 mg/kg every 3 weeks, and 4 doses are usually given as a course of treatment. DS8201 is a compound formed by coupling a trastuzumab analog with a chemotherapeutic agent. It is mainly used in the second-line treatment of patients with advanced metastatic breast cancer with Her2 expression, and the majority of Her2-positive patients with advanced breast cancer have a better remission rate after the use of this drug. The dosing regimen is 5.4 mg/kg every 3 weeks, and generally 4 doses are given as one treatment course. Gastrointestinal side effects such as nausea and vomiting, as well as the more serious side effects of interstitial pneumonitis, may occur with DS8201, and it must be applied under the supervision of a medical professional.