This is a prospective, randomised, controlled, multicentre study to compare the efficacy and safety between continuous or intermittent extension of adjuvant pyrotinib in invasive human epidermal growth factor receptor 2 (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.