Statistical analysis
A Simon minimax two-stage design was used to estimate the sample size, with a one-sided alpha of 5% and power of 80%. The null hypothesis (P0) was set as an ORR of 50%, referring to the ORR of pyrotinib monotherapy in HER2-positive ABC patients in a phase I studyData were collected using Electronic Data Capture System. Efficacy analyses were performed in eligible participants who received at least one efficacy evaluation, and safety analyses were carried out in all patients who received at least one dose of study treatment. The primary endpoint of ORR was estimated with a 95% confidence interval (CI). PFS and OS were estimated using the Kaplan-Meier method. All statistical analyses were performed using SAS (version 9.2).