A Multicenter and Real-world Analysis of RC48-ADC in Patients With HER2-positive or HER2-low Expressing, Locally Advanced or Metastatic Breast Cancer

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 , andtheestimated survival time was more than 2 months;
4. at least one extracranialmeasurable lesion or osteolytic or mixed bone metastasesinaccordance 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.