ERBB2 and breast cancer: HER2-positive BC and TNBC can achieve pCR rates of up to 45% (Boughey et al. 2014; Rouzier et al. 2005), but patients with HR-positive/HER2-negative tumors have PCR rates of only 0–18% after NAC (Torrisi et al. 2021), which is much lower than those of patients with the other two subtypes.