The purpose of this study is:~To explore the Response rate (RR) and progression-free survival(PFS) and safety of patients with recurrent metastatic breast cancer who received trastuzumab combined with pyrotinib in positive plasma HER2 amplification detected by digital PCR.~To explore the potential using of digital PCR in recurrent and metastatic breast cancer.
The hypothesis of this study is to discover the efficacy and safety of trastuzumab combined with pyrotinib in treating advanced breast cancer with HER2 positive, which is detected by digital PCR. It is a single-arm, multicenter phase II clinical study.~The purpose of this study is:~To explore the Response rate (RR) and progression-free survival(PFS) and safety of patients with recurrent metastatic breast cancer who received trastuzumab combined with pyrotinib in positive plasma HER2 amplification detected by digital PCR.~To explore the potential using of digital PCR in recurrent and metastatic breast cancer.