ERBB2 and breast cancer: Its research results showed that PD-L1 positive compared with PD-L1 negative patients with trastuzumab resistance and advanced HER2 positive breast cancer patients, the PD-1 inhibitor pabolizumab combined with trastuzumab could improve objective response rate(ORR) (15% vs. 0) and 1-year PFS (12% vs. 0), One-year OS (65% vs. 12%), and the clinical survival outcome is beneficial (54).