A Real-world Study of Inetetamab for First-line Treatment of MBC

Inclusion Criteria:

* Patients aged ≥18 years and ≤75 years;Patients aged ≥18 years and ≤75 years;
* Her2-positive invasive breast cancer confirmed by pathological examination met the following conditions:

Positive HER2 expression: Immunohistochemical staining (IHC) showed positive HER2 3+ and/or fluorescence in situ hybridization (FISH); Tumor staging: inoperable locally advanced or recurrent metastatic breast cancer; Patients with local recurrence must be confirmed by the investigator to be unable to undergo radical surgical excision.

* At least one measurable lesion was present according to RECIST1.1 criteria;
* The ECOG score is 0 to 1;
* No systematic antitumor therapy (except first-line endocrine therapy) has been received at the locally advanced stage (clinically inoperable) or at the stage of recurrence and metastasis;
* The functional level of major organs must meet the following requirements (no blood transfusion within 2 weeks prior to screening, no use of leukocyte enhancing and platelet enhancing drugs) :

  1. Blood routine: neutrophils (ANC) ≥1.5×109/L; Platelet count (PLT) ≥90×109/L; Hemoglobin (Hb) ≥90 g/L;
  2. Blood biochemistry: total bilirubin (TBIL) ≤ upper limit of normal value (ULN), known patients with Gilbert syndrome, TBIL≤2×ULN; Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤1.5×ULN, patients with liver metastasis required ALT and AST≤5×ULN; Alkaline phosphatase ≤2.5×ULN; Urea/urea nitrogen (BUN) and creatinine (Cr) ≤1.5×ULN;
  3. Cardiac ultrasound: left ventricular ejection fraction (LVEF) ≥50%;
  4. 12-lead electrocardiogram: Fridericia corrected QT interval (QTcF) \<470 msec;
* Expected survival ≥3 months;
* Participate in this study voluntarily, sign informed consent, have good compliance and be willing to cooperate with follow-up.

Exclusion Criteria:

* Known allergic history of drug components of the program;
* Patients judged unsuitable for systematic chemotherapy by researchers;
* Use of endocrine therapy drugs within 14 days before baseline;
* Patients with only bone or skin as target lesions;
* Other malignancies, excluding cured cervical carcinoma in situ, skin basal cell carcinoma or squamous cell carcinoma, within the previous 5 years;
* Peripheral neuropathy ≥ grade 3 according to CTCAE 5.0 criteria;
* Had received major surgical procedures or significant trauma within 4 weeks prior to randomization, or was expected to receive major surgical treatment;
* Serious heart disease or discomfort, including but not limited to:

heart failure or contraction dysfunction (LVEF \<50%) past medical history high risk or the need for treatment of angina or arrhythmia (such as second degree atrioventricular block type 2 or 3 degree atrioventricular block, ventricular tachycardia) clinical significance of heart valve disease ECG showed wall permeability myocardial infarction poorly controlled hypertension, systolic blood pressure\>150 mmHg and/or diastolic blood pressure\>100 mmHg

* Dysphagia, chronic diarrhea, intestinal obstruction and other factors affecting drug delivery and absorption;
* A history of immunodeficiency, including HIV infection, or other acquired, congenital immunodeficiency diseases, or a history of organ transplantation;
* Participated in other drug clinical studies within 4 weeks prior to screening;
* There is a third interstitial effusion (such as pleural fluid and ascites) that cannot be controlled by drainage or other methods;
* Pregnant or lactating women, women of childbearing age who are unable to take effective contraceptive measures throughout the trial period;
* Have a serious concomitant disease or other co-medical condition that interferes with planned treatment or any other condition that is not suitable for participation in the study, such as active hepatitis B, lung infection requiring treatment, etc.