Between July 2020 and August 2024, 301 HER2-positive MBC patients from five tertiary centers received the regimen until disease progression or unacceptable toxicity. Efficacy endpoints included progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR).

Inclusion Criteria:

• patients who underwent a biopsy of the metastatic site and were confirmed as having MBC
• patients who received inetetamab + pyrotinib + chemotherapy as metastasis therapy.

Exclusion Criteria:

• male patients or individuals with prior malignancy
• patients with prior or current enrollment in interventional clinical trials for MBC
• patients who received less than 2 cycles of treatment (6 weeks of inetetamab or 8 weeks of pyrotinib)
• patients who were lost to follow-up during the therapeutic process

Patients from five centers, clinical oncology school of fujian medical university, fujian provincial hospital, the first affiliated hospital of xiamen university, zhangzhou zhengxing hospital and the third affiliated people's hospital of fujian university of traditional chinese medicine