ERBB2 and breast cancer: In particular, HER2-low-positive breast cancer was associated with the lowest rate of pCR, followed by HER2-0 and HER2-positive tumors (pCR rates HER2-low-positive vs. HER2-0 vs. HER2-positive: 21.4% vs. 33.6% vs. 45.9%, respectively, p < 0.001 χ2 test), as shown in Fig. 2.