ERBB2 and breast cancer: Its phase II results showed that in HER2-positive, advanced, heavily pretreated breast cancer patients, the ORR of PD-L1-positive patients (n = 40, selected by PD-L1 22C3 pharmDx assay) was 15%, the median PFS was 2.7 months, the estimated 6-month PFS rate was 25%, and the 12-month PFS rate was 12%; the median OS has not been reached, and the 6-month and 12-month OS rates were estimated to be 87% and 65%, respectively.