Continuous or Intermittent Extension of Adjuvant Pyrotinib for Invasive HER2-positive Breast Cancer

Inclusion Criteria: * Aged ≥18; * Histologically confirmed invasive HER2 positive breast cancer; * Duration from random time to the last use of trastuzumab or T-DM1 ≤3 years; * Performance Status- Eastern Cooperative Oncology Group (ECOG) 0-1; * Adequate organ functions. Exclusion Criteria: * Metastatic disease (Stage IV); * Gross residual disease remaining after mastectomy or positive margins after breast-conserving surgery; * Subjects that are unable to swallow tablets, or dysfunction of gastrointestinal absorption; * Treated or treating with anti-HER2 tyrosine kinase inhibitor; * Less than 4 weeks from the last clinical trial; * History of immunodeficiency, including HIV-positive, suffering from other acquired, congenital immunodeficiency disease, or history of organ transplantation; * Female patients who are pregnancy, lactation or women who are of childbearing potential tested positive in baseline pregnancy test; Female patients of childbearing age that are reluctant to take effective contraceptive measures throughout the trial period; * Evidence of significant medical illness that in the investigator's judgment will substantially increase the risk associated with the subject's participation in and completion of the study.