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.