Evaluate the efficacy and safety of Disitamb Vedotin in patients with HER2-positive or HER2-low expressing, locally advanced or metastatic breast cancer

The main goal of this clinical trial is to examinie the utilization of RC48 in different HER2 statuses, elucidating its clinical outcomes and safety, and investigating the factors that influence its clinical efficacy. The primary endpoint was the objective response rate (ORR) assessed by the primary researcher. Secondary endpoints included progression-free survival (PFS), overall survival (OS), disease control rate (DCR), time to progression, and safety.

Inclusion Criteria:

1. histopathologically or imaging-confirmedlocally advanced or metastatic breast cancer ;
2. HER2-positive or low status;
3. the function of major organswas normal, no treatmentcontraindications , andthe estimated survival time was more than 2 months;
4. at least one extracranialmeasurable lesion or osteolytic or mixed bone metastases inaccordance with the Response Evaluation Criteria in Solid Tumors v. 1.1 (RECIST 1.1);
5. the clinical data were complete and traceable.

Exclusion Criteria:

1. age <18 ye ars old;
2. other concurrent cancers;
3. patients who rece ived RC48 as a neoadjuvant or adjuvant regimen；
4. Incomplete medical data.

Patients with HER2-positive or HER2-low expressing, locally advanced or metastatic breast cancer were eligible and received RC48 2.5 mg/kg every two weeks alone or combined with drugs with different anti-tumor mechanisms, such as immune checkpoint inhibitors (ICIs), tyrosine kinase inhibitors (TKIs) and antiangiogenic compounds.