A Study to Evaluate the Safety and Effectiveness of Trastuzumab Emtansine (T-DM1) as Therapy in Chinese Participants With HER2 Positive Advanced Breast Cancer

Inclusion Criteria:

• Diagnosed with HER2-positive, unresectable locally advanced or metastatic breastcancer before the start of T-DM1 treatment

• Had prior treatment for breast cancer which must contain a taxane and trastuzumab

• Get the treatment of T-DM1 for the first time after diagnosis of breast cancer

Exclusion Criteria:

• Patients not receiving treatment for HER2-positive breast cancer with T-DM1according to standard of care and in line with the current summary of productcharacteristics (SPC)/local labeling

• Has been previously treated with T-DM1 before current clinical visit

• Currently participating in any clinical trials

• Previously participated in any clinical trials investigating anti-HER2 drug within 1year of the initiation of T-DM1