ERBB2 and breast cancer: More recently, in the phase 3 KATHERINE trial, T-DM1 was shown to improve the 3-year disease-free survival rate from 77% to 88.3% (HR, 0.50; P < 0.001) when compared to trastuzumab for the treatment of patients with residual invasive HER2+ breast cancer after neoadjuvant therapy.