ERBB2 and breast cancer: However, a phase II trial (KATE2), in which 202 patients with HER2-positive advanced breast cancer were randomized into an atezolizumab plus T-DM1 (trastuzumab emtansine) group and a T-DM1 monotherapy group, showed an mPFS of 8.2 months in a combined therapy group versus 6.8 months in T-DM1 alone group in the intention-to-treat population.