A Phase II Study of SHR-A1811 Combined With Radiotherapy in HER2-positive and HER2-low Breast Cancer Brain Metastases

Inclusion Criteria

• •1. Pathologically confirmed HER2 positive (IHC 3+ or IHC 2+/FISH+)or HER2-low(IHC1+ or 2+/FISH-) advanced breast cancer
• •2. Age\>18 years.
• •3. newly diagnosed Brain metastases confirmed by enhanced brain MRI. Metastases number less than 6.
• •4. No more than four lines of previous advanced therapy
• •5. Life expectancy of more than 3 months
• •6. There were no known or suspected leptomeningeal brain metastases
• •7. The interval from previous therapy was more than 2 weeks, and acute toxicity from previous therapy had to resolve to grade 1 or less
• •8. The use of mannitol, bevacizumab, or hormone therapy was allowed before enrollment, but the dose was stable for at least a week without the need for an increment
• •9. Screening laboratory values must meet the following criteria( and should be obtained within 28 days prior to registration):
• •Absolute Neutrophil Count (ANC) ≥ 1.5 x 109/L, Platelets≥ 90 x 109/L, Hemoglobin ≥ 90 g/L Aspartate aminotransferase/alanine aminotransferase (AST/ALT) ≤2.5 x ULN without liver metastasis,≤ 5 x ULN with liver metastases Serum BUN and creatinine ≤ 1.5 x Upper Limit of Normal (ULN) LVEF ≥ 50% QTcF \< 480 ms INR≤1.5×ULN，APTT≤1.5×ULN 10.Signed the informed consent form prior to patient entry