To evaluate the efficacy and safety of Disitamab vedotin (RC48-ADC) as salvage treatment in patients with HER2-low advanced breast cancer who have received up to one previous chemotherapy for recurrent or metastatic disease without previous use of antibody-drug conjugate.

Subjects with HER2-low advanced breast cancer were treated with Disitamab vedotin as salvage treatment. ORR, PFS, OS and AE were assessed during the trial. HER2-low status is defined as IHC1+ or IHC2+ with negative FISH test.

Inclusion Criteria:

• Female patients aged ≥18 years
• Expected survival ≥12 weeks
• ECOG 0-1
• Histologically confirmed invasive advanced or metastatic breast cancer that is incurable and unresectable
• At least one measurable lesion according to the RECIST 1.1
• No history of antibody-drug conjugate use
• Up to one previous chemotherapy for advanced disease
• Available hormone receptor status. Hormone receptor-positive subjects are allowed to receive no more than two previous endocrine therapy for advanced disease
• HER2-low tumors, defined as IHC1+ or IHC2+ with negative FISH test; or HER2-ultralow tumors, defined as incomplete and faint membrane staining in >0 but ≤10% of tumor cells
• Adequate organ function

Exclusion Criteria:

• History of thromboembolic events
• Uncontrolled systemic diseases, including diabetes, hypertension, interstitial lung disease, cirrhosis, etc.
• Active infections requiring systemic treatment
• Pregnant or lactating
• Presence of brain metastases and/or carcinomatous meningitis

Study protocol and SAP are to be shared with other researchers.

starting 6 months after publication

IPD can be accessed from the corresponding author on reasonable request.