Stage I HER2 Positive Invasive Breast Cancer De-escalation Study(IRIS)

In IRIS-A cohort, patients who met the inclusion criteria(ER，PR\<10%, T≤2cm or ER,PR ≥10% 1cm\<T≤2cm）would be given capecitabine for 6 cycles with standard trastuzumab for 1 year, in which HR+ patients would be given endocrine therapy for 5 years.

In IRIS-B cohort, patients who met the inclusion criteria(ER,PR ≥10% T≤1cm) would be given endocrine therapy (premenopausal: tamoxifen or toremifene; postmenopausal: letrozole or anastrozole or exemestane) combined with standard trastuzumab for 1 year and complete endocrine therapy for 5 years.