However, in a subgroup analysis, T-DM1 plus atezolizumab had a higher 1-year OS compared to T-DM1 plus placebo in patients with PD-L1+, HER2+ advanced breast cancer (94.3% vs. 87.9%, HR=0.55; 95% CI: 0.22-1.38). This evidence concerns the gene ERBB2 and breast cancer.