ERBB2 and triple-negative breast carcinoma: Atezolizumab is also approved for PD-L1-positive triple-negative breast cancer, but a phase II clinical trial (KATE2) testing T-DM1 + atezolizumab vs. T-DM1 alone in trastuzumab-resistant PD-L1-positive HER2-positive advanced breast cancer showed only a modest improvement in progression-free survival and, worryingly, more adverse events, including one treatment-related death [55].