ERBB2 and breast carcinoma: Furthermore, adding atezolizumab to T-DM1 for patients with locally advanced or metastatic HER2-positive breast cancer who had previously undergone treatment with trastuzumab and paclitaxel-based therapy, led to improved progression-free survival (PFS) in PD-L1-positive patients exhibiting TILs of at least 5% (28).