ERBB2 and neoplasm: HR-/HER2- tumors were more likely to respond if they showed an increased Ki67 level: a significantly higher pCR rate was seen in tumors with > 20% positive nuclei (63.6% vs. 0%, P < 0.0001, χ2 test), and an increase of 10% of Ki67-labeled tumor cells equaled a hazard ratio of 1.92 (P = 0.006, Table 3).