ERBB2 and breast cancer: To evaluate the effectiveness of T-DM1 in the treatment of recurrent or metastatic HER2-positive breast cancer, the phase IIIb clinical trial, also known as KAMILLA (ClinicalTrials.gov identifier NCT01702571), was conducted in a cohort of 2185 patients with HER2-positive metastatic breast cancer, including those with brain metastases.