In the PANACEA phase Ib/II, the anti-PD-1 pembrolizumab in combination with trastuzumab was explored in metastatic HER2+ BC patients who had progressed to trastuzumab.29 Objective response rates (ORR) of 15.2% in the 40 PD-L1-positive BC patients and 0% in the 12 PD-L1-negative patient cohort were reported. Here, ERBB2 is linked to breast cancer.