Conclusion
toxicities, HR-positive
In conclusion, our preliminary results suggested that pyrotinib plus letrozole is feasible for the first-line treatment of patients with HR-positive and HER2-positive MBC, with a median PFS of 13.7 months. The toxicities were manageable. Subsequent large-scale trials are required to assess the efficacy of pyrotinib plus AI and other anti-HER2 agents or CDK4/6 inhibitors for HR-positive and HER2-positive MBC.