Inclusion Criteria:  Histologically confirmed invasive HER2-positive breast cancer. The baseline left ventricular ejection fraction >55%. Living at high altitude area （>2000 meters）for at least 10 years. ECOG score 0-2. Expected survival time ≥ 12 months.  Exclusion Criteria:  Patients with previous breast cancer or other malignant tumor within 5 years. Patients who had accepted previous anti-HER2 or anthracyclines-based therapy. Patients with severe heart disease or discomfort. Patients who are pregnant. Patients with other conditions considered not suitable to be enrolled by the investigator.