Herceptin is mainly used for the treatment of breast cancer and has a preventive effect on the recurrence of early stage breast cancer. It also has relatively good efficacy in the control and treatment of advanced breast cancer, which has been confirmed by clinical trials. Also recent studies have shown that it can treat advanced metastatic lung cancer. Herceptin has a conditional application and is generically known as trastuzumab for patients with HER2-positive breast cancer or gastric cancer. It may be taken clinically in early stage breast cancer, before or after surgery, called neoadjuvant chemotherapy or adjuvant chemotherapy, or it may be used in late stage for controlling the progression of breast cancer. Herceptin is a targeted drug that can target HER2-positive patients in breast cancer, which can control tumor progression and prevent tumor recurrence in this group of patients. Herceptin may cause adverse reactions or side effects, including immunogenic reactions, mainly in the form of increased heart rate or difficulty in breathing, which may lead to shock in severe cases. It may cause some heart-related adverse reactions, so heart function should be monitored regularly during the drug administration. There are some other adverse reactions to Herceptin that should be used under the guidance of an oncologist or pharmacist to facilitate the safety of the drug and to help the drug work best. For more information about the precautions and precautions for the use of Herceptin, please refer to the instruction manual and use under the guidance of your doctor or pharmacist.