Multivariate analyses revealed that a HR-negative status and higher levels of Ki-67 (> 20%) were independent predictive factors for achieving pCR in patients with early-stage HER2-positive breast cancer after being treated with the neoadjuvant combination of pertuzumab, trastuzumab and CT (Odds ratio [OR] = 2.143; 95% confidence interval [CI] 1.321–3.477, and OR = 1.931; 95% CI 1.082–3.445, respectively) (Table 3). This evidence concerns the gene MKI67 and breast cancer.