A ReaL World Study of DS-8201

Inclusion criteria

• Male or female aged 18 or above;
• The Eastern Cooperative Oncology Group (ECOG) physical condition score of the United States is ≤2;
• HER2 positive (IHC 3+ or IHC 2+ and ISH+) confirmed by tumor histology or cytology, and having received one or more anti-HER2 drug treatments previously; Or low expression of HER2 confirmed by tumor histology or cytology (IHC 1+ or IHC 2+ and ISH-), and having received at least one systemic treatment in the metastatic disease stage previously, or unresectable or metastatic breast cancer that relapsed during adjuvant chemotherapy or within 6 months after the completion of adjuvant chemotherapy;
• Receive goldtrastuzumab treatment in the advanced stage;
• During the study period, voluntarily abide by this trial protocol and receive regular follow-ups;
• All women of childbearing age, fertile men or their spouses who have no plans for fertility or sperm donation throughout the trial period until 6 months after the last dose, or who voluntarily take effective contraceptive measures.

Exclusion criteria

• Pregnant or lactating women;
• Those with acute or chronic infections, or those with other serious diseases at the same time, are judged by the researchers as unsuitable for this study;
• Having suffered from other malignant tumors within 5 years (excluding the following situations: cured basal cell carcinoma of the skin, carcinoma in situ of the cervix, and papillary thyroid carcinoma; A second primary cancer that has been completely cured and has no recurrence within five years; Researchers have clearly identified which primary tumor source the metastatic foci belong to.
• Those with mental illness or mental disorders, poor compliance and inability to cooperate and describe treatment responses;
• Those with severe organic diseases or major organ failure, such as decompensated heart, lung, liver or kidney failure, which makes them unable to tolerate treatment;
• Patients allergic to trastuzumab;
• Patients who changed their treatment regimens after trastuzumab treatment due to reasons other than disease progression or intolerable adverse reactions;
• The researcher believes that the patient has other circumstances that make them unsuitable for participating in this study