In 2022, the results of the DESTINY-Breast04 study, which enrolled patients with HER2-overexpressing advanced breast cancer (mBC), were published and found that all patients receiving T-DXd treatment had significantly longer PFS and OS, and rapidly changed international authoritative guidelines such as NCCN and ESMO in a short period of time, and was approved as the first HER2-targeted therapy for patients with HER2-low mBC (22). The gene discussed is ERBB2; the disease is breast cancer.