PD-L1 IHC
PD-L1 IHC was performed using the PD-L1 IHC 22C3 pharmDx kit (Dako) on the Dako ASL48 platform according to manufacturer recommendations. HER2 IHC was performed using the HER2/neu kit (Ventana) following the standard preprogrammed staining protocol. The anti-PD-L1 antibody (clone: 22C3) and anti-HER2 antibody (clone: 4B5) were provided already diluted at an unspecified ratio in the kit.