ERBB2 and neoplasm: Biomarker study on pre-treatment HER2 amplification in plasma circulating tumor DNA by next-generation sequencing and PD-L1 expression on archival tumor tissue by IHC (22C3 pharmDx) showed that both HER2 amplification and PD-L1 positivity predicted RR (24% versus 0% [p = 0.0655] and 36% versus 5% [p = 0.0367], respectively) [25].